Did you ever find the bolt you dropped? I wonder if that is wreaking havoc somewhere? Could it have jammed against the wiring harness somewhere and causing a short?
It seems as though you have an intermittent problem. Your fuel trims should go double-digit positive to add fuel in an attempt to correct the lean condition. These codes get triggered when the system can no longer add enough fuel to pull the engine toward stoich based upon the feedback from the O2s. I think the limit is somewhere around +25, and you are seeing your trims in the low single digits, where they should be.
Since you are getting both codes, both your O2s
should be ok, and the problem is most likely common to both banks. (The power circuit is common to both O2s.) That leaves an intermittent vacuum leak, MAF issue, or an intermittent fuel delivery problem.
Check for leaks on the oil cap, dip stick, and PCV Valve / lines.
I've seen these codes pop up with a failing EVAP purge solenoid on other platforms. The diaphragm in the solenoid leaks vacuum when the PCM commands EVAP purge. This makes the problem somewhat intermittent.
Can you monitor your fuel pressure and EVAP Purge Solenoid duty cycle and see what they are doing when the lean condition occurs?
Here is what the Ford PC/ED says for these codes. Lots of possibilities. You can skip the EGR and Secondary Air System, as these engines don't have them.
P0171 - System Too Lean (Bank 1) Description: The adaptive fuel strategy continuously monitors the fuel delivery hardware. The test fails when the adaptive fuel tables reach a rich calibrated limit. Refer to Section 1,
Powertrain Control Software Fuel Trim for more information.
Possible Causes: Fuel System:
- Ethanol content in the fuel
- Damaged or leaking fuel pulse damper
- Fuel filter plugged or dirty
- Damaged or worn fuel pump
- Leaking fuel pump check valve
- Leaking/contaminated fuel injectors
- Low fuel pressure or running out of fuel
- EVAP canister purge valve is leaking when the canister is clean
- Fuel supply line restricted
- Fuel rail pressure sensor bias
Air Induction System:
- Air leaks after the mass air flow (MAF) sensor
- Vacuum leaks
- Positive crankcase ventilation (PCV) system is leaking or the valve is stuck open
- Improperly seated engine oil dipstick
- Air induction turbulence due to incorrect air filter
Exhaust System:
- Exhaust leaks in the exhaust manifold gasket or mating gaskets before or near the HO2S
EGR System:
- Vacuum hose disconnected on exhaust gas recirculation (EGR) system module (ESM) applications
- EGR valve tube/gasket leak
- EVR solenoid vacuum leak
Secondary Air Injection:
- Damaged secondary air injection system or a mechanically stuck valve
Air Measurement System:
- Damaged or contaminated MAF sensor
Diagnostic Aids: View the Freeze Frame Data to determine the operating conditions when the DTC was set. Observe the LONGFT1 and LONGFT2 PIDs. Refer to Section 2,
Adaptive Fuel DTC Diagnostic Techniques for more information and the appropriate pinpoint test for specific concern identification.
Application Key On Engine Off Key On Engine Running Continuous Memory All — — GO to Pinpoint Test
H .
P0174 - System Too Lean (Bank 2) Description: See the description for DTC P0171.
Possible Causes: See the possible causes for DTC P0171.
Diagnostic Aids: See the diagnostic aids for DTC P0171.
Application Key On Engine Off Key On Engine Running Continuous Memory All — — GO to Pinpoint Test
H .
2006 PCED Gasoline Engines
SECTION 5: Pinpoint Tests
Procedure revision date: 10/26/2007
H: Fuel Control
H: Introduction
H1 CHECK FOR DTCS
Are DTCs P0171, P0172, P0174, P0175, P2195, P2196, P2197, P2198, P2270, P2271, P2272, P2273, P2274, or P2275 present?
Yes No For DTCs P2270, P2271, P2272, P2273, P2274 or P2275, GO to
H32 .
For DTCs P0171, P0174, P2195 or P2197, GO to
H2 .
For DTCs P0172, P0175, P2196 or P2198, GO to
H8 . For all others, GO to Section 4,
Diagnostic Trouble Code (DTC) Charts and Descriptions .
H2 DTCS P0171, P0174, P2195 OR P2197: LEAN SYSTEM DTCS
- Note: Do not clear the DTCs or reset the keep alive memory (KAM).
- Access the PCM and record the ECT PID from the freeze frame data. The freeze frame data is used to recreate the concern.
- Retrieve and record the self-test DTCs.
Are any DTCs present other than the following: P0171, P0174, P2195 or P2197?
Yes No DISREGARD the current diagnostic trouble code (DTC) at this time. DIAGNOSE the next DTC. GO to Section 4,
Diagnostic Trouble Code (DTC) Charts and Descriptions . GO to
H3 .
H3 CARRY OUT A VISUAL INSPECTION ON THE INTAKE AIR SYSTEM AND ALL VACUUM HOSES
- Key in OFF position.
- Check the intake air system for leaks, obstructions, and damage.
- Inspect the entire length of all the vacuum hoses for:
- proper connections
- damage or cracks
- damaged or cracked vacuum tees
- Verify the integrity of the positive crankcase ventilation (PCV) system.
- Verify the proper PCV valve part number.
Is a concern present?
Yes No GO to
H6 . GO to
H4 .
H4 CHECK FOR THE PRESENCE OF A VACUUM LEAK
- Note: Fuel trim values at idle are more sensitive to a vacuum leak. The vacuum leak (unmetered air) represents a larger portion of the total air flow at idle than at part throttle.
Note: The barometric pressure (BARO) PID is not a recommended PID to monitor when diagnosing a vacuum leak. Barometric pressure is calculated during high engine load, when the vacuum leak represents a small portion of the total air flow.
Note: When calculating the total fuel correction in the following steps, if LONGFT1 equals +13% and SHRTFT1 equals +23%, the total fuel correction for bank 1 equals +36%. If LONGFT2 equals +24% and SHRTFT2 equals -3% the total fuel correction for bank 2 equals +21%.
Note: If the freeze frame ECT PID is available, stabilize the engine at the temperature recorded by the freeze frame ECT PID. If the freeze frame ECT PID is not available, maintain the engine coolant temperature between 82°C - 101°C (180°F - 215°F) and the intake air temperature less than 46°C (115°F).
- Key ON, engine running.
- Access the PCM and monitor the ECT, CHT and IAT PIDs.
- Access the PCM and monitor the LONGFT1, SHRTFT1, LONGFT2 and SHRTFT2 PIDs.
- Allow the engine to stabilize at the temperature necessary to recreate the concern.
- Mathematically add and record the LONGFT PID value to the SHRTFT PID value for each bank, for a total fuel correction at idle.
- Increase the engine speed to 3,500 RPM for 10 seconds. For vehicles with electronic throttle control (ETC), increase the engine speed to the maximum RPM without activating RPM limiting.
- Record the LONGFT1, SHRTFT1, LONGFT2, and SHRTFT2 PID values.
- Mathematically add and record the LONGFT PID value to the SHRTFT PID value for each bank, for a total fuel correction at 3,500 RPM or the maximum allowable RPM for vehicles with ETC.
Is the total fuel correction value difference, between idle and 3,500 RPM or the maximum allowable RPM for vehicles with ETC, less than 15 percent?
Yes No No vacuum leak is present.
For DTCs P0171, P0174, P2195, or P2197 with a secondary air injection (AIR) system, GO to
H7 .
For DTCs P0171 or P0174 without a secondary air injection (AIR) system, GO to
H16 .
For DTCs P2195 or P2197 without a secondary air injection (AIR) system, GO to
H10 . GO to
H5 .
H5 LOCATE THE VACUUM LEAK
- CAUTION: Do not clamp or pinch a hard plastic hose. Use a vacuum cap or equivalent to restrict the hose.
Note: Restricting the EVAP vapor hose while the EVAP emission canister is purging may shift the SHRTFT. Carry out a visual inspection as necessary.
Note: When monitoring for a decrease in the SHRTFT PIDs in the following steps, if SHRTFT1 equals +15% and the hose is restricted, SHRTFT1 decreases to -7%. The total decrease in the SHRTFT PIDs equals 22%.
- Locate the vacuum tees for the intake air and PCV systems.
- Access the PCM and monitor the SHRTFT1 and SHRTFT2 PIDs.
- Restrict the vacuum lines one at a time for 30 seconds. If a vacuum leak is present, the SHRTFT PID values decrease as the hose is restricted.
Is the decrease in the SHRTFT PIDs greater than 15 percent when one of the vacuum hoses is restricted?
Yes No GO to
H6 . INSPECT the intake air system for a vacuum leak in the intake manifold or intake gaskets. REPAIR as necessary.
For repair verification, GO to
H6 .
H6 VACUUM LEAK REPAIR VERIFICATION
- Note: If the freeze frame ECT PID is available, stabilize the engine at the temperature recorded by the freeze frame ECT PID. If the freeze frame ECT PID is not available, maintain the engine coolant temperature between 82°C - 101°C (180°F - 215°F) and the intake air temperature less than 46°C (115°F).
- Access the PCM and monitor the SHRTFT1 and SHRTFT2 PIDs.
- Allow the engine to stabilize at the temperature necessary to recreate the concern.
- Record the SHRTFT1 and SHRTFT2 PID values.
- Key in OFF position.
- Repair the vacuum leak.
- Key ON, engine running.
- Allow the engine to stabilize at the temperature necessary to recreate the concern.
- Access the PCM and monitor the SHRTFT1 and SHRTFT2 PIDs.
- Compare the recorded SHRTFT PID values, prior to the vacuum leak repair, to the current SHRTFT PID values.
Is the decrease in the SHRTFT PIDs greater than 15 percent?
Yes No RESET the keep alive memory (KAM). REFER to Section 2,
Resetting The Keep Alive Memory (KAM) .
REPEAT the self-test. A vacuum leak is still present.
GO to
H5 .
H7 CHECK FOR SECONDARY AIR LEAKS
Note: An HO2S always lean condition can be caused by:
- leaks in the hoses from the secondary air injection pump to the engine.
- secondary air diverted upstream of the HO2S.
- Disconnect the secondary air injection hose(s) from the engine and the plug side of the secondary air injection system.
- Key ON, engine running.
- Carry out the self-test.
Are DTCs P0171, P0174, P2195 or P2197 present?
Yes No For DTCs P0171 or P0174, GO to
H16 .
For DTCs P2195 or P2197, GO to
H10 . GO to
HM18 .
H8 DTCS P0172, P0175, P2196 OR P2198: RICH SYSTEM DTCS
- Note: Do not clear the DTCs or reset the keep alive memory (KAM).
- Access the PCM and record the freeze frame data.
- Retrieve and record the self-test DTCs.
Are any DTCs present other than the following: P0172, P0175, P2196 or P2198?
Yes No DISREGARD the current diagnostic trouble code (DTC) at this time. DIAGNOSE the next DTC. GO to Section 4,
Diagnostic Trouble Code (DTC) Charts and Descriptions . GO to
H9 .
H9 INSPECT THE ENTIRE INTAKE AIR SYSTEM FOR DEBRIS, BLOCKAGE OR OTHER DAMAGE
- Check the intake air system for obstructions, restrictions, and damage.
- Check the throttle plate for obstructions or sludge.
- Check the air filter element and housing for blockage.
Is a concern present?
Yes No REPAIR as necessary.
CLEAR the DTCs. REPEAT the self-test. For DTCs P0172 or P0175, GO to
H16 .
For DTCs P2196 or P2198, GO to
H14 .
H10 CHECK THE HO2S AND SIGRTN CIRCUIT(S) FOR AN OPEN IN THE HARNESS
- Key in OFF position.
- Disconnect the HO2S related to the current DTC.
- PCM connector disconnected.
- Measure the resistance between:
( + ) HO2S Connector, Harness Side ( - ) PCM Connector, Harness Side HO2S Signal HO2S Signal SIGRTN SIGRTN
Are the resistances less than 5 ohms?
Yes No GO to
H11 . REPAIR the open circuit. CLEAR the DTCs. REPEAT the self-test.
H11 CHECK THE HO2S CIRCUIT FOR A SHORT TO SIGRTN IN THE HARNESS
- Measure the resistance between:
( + ) HO2S Connector, Harness Side ( - ) HO2S Connector, Harness Side HO2S Signal SIGRTN
Is the resistance greater than 10K ohms?
Yes No GO to
H12 . REPAIR the short circuit. CLEAR the DTCs. REPEAT the self-test.
H12 CHECK THE HO2S CIRCUIT FOR A SHORT TO GROUND IN THE HARNESS
- Measure the resistance between:
( + ) HO2S Connector, Harness Side ( - ) HO2S Signal Ground
Is the resistance greater than 10K ohms?
Yes No GO to
H13 . REPAIR the short circuit to GND. CLEAR the DTCs. REPEAT the self-test.
H13 HO2S CIRCUIT TEST (WITH LEAN DTCS)
- PCM connector connected.
- Connect a 5 amp fused jumper wire between the following:
Point A HO2S Connector, Harness Side Point B HO2S Connector, Harness Side HO2S Signal VPWR
- Key ON, engine OFF.
- Access the PCM and monitor the HO2S Signal PID.
Is the voltage greater than 1.3 V?
Yes No GO to
H16 . GO to
H42 .
H14 HO2S CIRCUIT TEST (WITH RICH DTCS)
- Disconnect the HO2S related to the current DTC.
- Key ON, engine OFF.
- Access the PCM and monitor the HO2S Signal PID.
Is the voltage less than 0.2 V?
Yes No GO to
H16 . GO to
H15 .
H15 CHECK THE HO2S CIRCUIT FOR A SHORT TO THE VPWR OR HEATER IN THE HARNESS
- Key in OFF position.
- PCM connector disconnected.
- Measure the resistance between:
( + ) PCM Connector, Harness Side ( - ) PCM Connector, Harness Side HO2S Signal HO2S Heater HO2S Signal VPWR
Are the resistances greater than 10K ohms?
Yes No GO to
H42 . REPAIR the short circuit. CLEAR the DTCs. REPEAT the self-test.
H16 CHECK THE FUEL PRESSURE
- WARNING: WHEN CHECKING THE FUEL SYSTEM REMEMBER THAT THE FUEL SYSTEM MAY STILL BE PRESSURIZED WHEN THE ENGINE IS SWITCHED OFF. ALWAYS FOLLOW THE INSTRUCTIONS RELATED TO FUEL SYSTEM PRESSURE RELIEF. ALL FUEL HANDLING SAFETY PRECAUTIONS MUST BE OBSERVED. FAILURE TO FOLLOW THESE INSTRUCTIONS MAY RESULT IN PERSONAL INJURY.
Note: For vehicle specific fuel pressure ranges, refer to the Fuel System Specification Chart in pinpoint test HC.
- Remove the jumper wire(s).
- HO2S connector connected.
- Relieve the fuel pressure. Refer to the Workshop Manual Section 310-00, Fuel System for the Fuel System Pressure Release procedure.
- Mechanical fuel pressure gauge connected.
- Pressurize the fuel system. Refer to the Workshop Manual Section 310-00, Fuel System for the Fuel System Pressure Release procedure to pressurize the fuel system.
- Key ON, engine running.
- Allow the fuel pressure to stabilize.
- Key in OFF position.
- Key ON, engine running.
- Access the PCM and control the FP PID.
- Run the fuel pump to obtain maximum fuel pressure.
Is the fuel pressure within range for the vehicle being diagnosed?
Yes No GO to
H17 . GO to Pinpoint Test
HC .
H17 CHECK THE FUEL SYSTEM FOR PRESSURE STABILITY - FAST LEAKDOWN
- Note: When the fuel pump is commanded off, the fuel pressure may substantially decrease and then stabilize.
Note: During output state control, the fuel pump stays commanded on for only about 5 seconds.
- Key in OFF position.
- Key ON, engine OFF.
- Access the PCM and control the FP PID.
- Run the fuel pump to obtain maximum fuel pressure.
- Command the fuel pump off.
- Allow the fuel pressure to stabilize.
- Record the stabilized reading.
- Monitor the fuel pressure for 10 seconds.
Does the fuel pressure remain within 34 kPa (5 psi) of the recorded reading after 10 seconds?
Yes No GO to
H19 . GO to
H18 .
H18 CHECK FOR AN EXTERNAL FUEL LEAK
- Inspect the fuel tank, lines, and filler pipe for a fuel leak.
Is a concern present?
Yes No REPAIR as necessary.
REFER to the fuel system WARNING information at the beginning of Pinpoint Test HC. GO to Pinpoint Test
HC .
CLEAR the DTCs. REPEAT the self-test. GO to
H26 .
H19 CHECK THE FUEL SYSTEM FOR PRESSURE STABILITY - SLOW LEAKDOWN
- Continue to monitor the fuel pressure for 1 minute.
Does the fuel pressure remain within 34 kPa (5 psi) of the recorded reading (MRFS) or greater than 275 kPa (40 psi) (ERFS) after 1 minute?
Yes No GO to
H20 . GO to
HC13 .
H20 CHECK THE SEPARATION LEVEL OF THE ETHANOL/WATER MIXTURE AND GASOLINE IN THE FUEL
- Note: This step requires the use of a locally obtained 200 ml beaker and a 25 ml graduated cylinder.
Note: After approximately 3 minutes of standing, the ethanol and water mixes together and settles to the bottom of the 25 ml graduated cylinder. The gasoline rises to the top.
- Fill the 200 ml beaker with 5 ml of clean water.
- Use the pressure relief valve on the mechanical fuel gauge to drain 22 ml of fuel into an approved clean container.
- Pour 20 ml of fuel from the approved clean container into the 25 ml graduated cylinder.
- Add enough water from the 200 ml beaker to the 25 ml graduated cylinder to bring the total volume of liquid to 24 ml.
- Insert a stopper plug in the opening of the 25 ml graduated cylinder.
- Firmly hold the stopper in place and shake the 25 ml graduated cylinder to mix the water and fuel.
- Allow the liquid to stand and separate for approximately 3 minutes.
- Record the separation level from the 25 ml graduated cylinder where the ethanol/water mixture and gasoline meet.
Did the ethanol/water mixture and gasoline separate?
Yes No GO to
H21 . COMPLETE all steps before continuing. The ethanol/water mixture will separate from the gasoline. If the fuel does not appear to separate, then the fuel is either 100% ethanol or a mixture of ethanol and water.
H21 CALCULATE THE PERCENTAGE OF ETHANOL IN THE FUEL
- Note: Use the illustration as an example for calculating the percentage of ethanol in the following steps. If the separation level is at 14 ml the calculation becomes; 14 minus 4, then multiply by 5 to equal 50. The percentage of ethanol in the fuel is 50%.
- Key in OFF position.
- Take the recorded separation level from the previous step and subtract the amount of water added.
- Multiply the new value by 5. This new value is the percentage of ethanol in the fuel.
Item Number Description 1 Stopper 2 Gasoline 3 Separation Point at 14 ml 4 Ethanol/Water Mixture
- Record the calculated percentage of ethanol in the fuel.
Is any ethanol present in the fuel?
Yes No For flex fuel vehicles, GO to
H22 .
For all others, GO to
H25 . GO to
H26 .
H22 COMPARE THE FF PID TO THE CALCULATED PERCENTAGE OF ETHANOL
- Note: When determining if the FF PID value is within 50% of the calculated percentage of ethanol, if the calculated percentage of ethanol value is 40% then the PID value should be between 0 - 90%. The PID value cannot be less than zero.
- Key ON, engine OFF.
- Access the PCM and monitor the FF PID.
- Compare the FF PID to the calculated percentage of ethanol.
Is the FF PID value within 50% of the calculated percentage of ethanol?
Yes No GO to
H26 . GO to
H23 .
H23 RESET THE PERCENT ETHANOL PARAMETER IN THE PCM
- Note: Certain customer fueling practices such as only fueling with small amounts of fuel or repeatedly switching between gasoline and an ethanol blend greater than E15 may prevent the PCM from learning the correct ethanol content in the fuel.
- Reset the keep alive memory (KAM). Refer to Section 2, Resetting The Keep Alive Memory (KAM) .
- Key ON, engine running.
- Access the PCM and monitor the FF_LRN PID.
- Drive the vehicle approximately 11.3 km (7 miles) or until the FF_LRN PID indicates yes.
Is the PID state YES?
Yes No GO to
H24 . GO to
H42 .
H24 COMPARE THE UPDATED FF PID TO THE CALCULATED PERCENTAGE OF ETHANOL
- Key in OFF position.
- Key ON, engine OFF.
- Access the PCM and monitor the FF PID.
Is the FF PID value within 50% of the calculated percentage of ethanol?
Yes No RETURN the vehicle to the customer. ADVISE the customer of the correct fueling practices when using flex fuel. REFER to the Owner's Literature for additional information. ADVISE the customer to continue to use the same fuel for the next 2-3 refuels. This practice helps to verify the PCM is learning the correct percentage of ethanol in the fuel. A fuel system concern may be present, which prevents the PCM from learning the correct percentage of ethanol in the fuel,
GO to
HC13 .
H25 DETERMINE IF THE PERCENTAGE OF ETHANOL IN THE FUEL IS LESS THAN 25%
- Check the recorded calculated percentage of ethanol in the fuel.
Is the calculated percentage of ethanol in the fuel less than 25%?
Yes No GO to
H26 . REPAIR as necessary. ADVISE the customer of the correct fuel type required for this vehicle. REFER to the Owner's Literature for additional information.
CLEAR the DTCs. REPEAT the self-test.
H26 FLOW TEST
- Key in OFF position.
- PCM connector connected.
- Flow test the injector using the fuel injector tester.
Is the flow rate for each injector within specification?
Yes No For DTCs P0171, P0172, P0174 or P0175, GO to
DC28 .
For DTCs P2195 or P2197, GO to
H27 .
For DTCs P2196 or P2198, GO to
H28 . INSTALL a new fuel injector. REFER to the Workshop Manual Section 303-04, Fuel Charging and Controls.
RESET the keep alive memory (KAM). REFER to Section 2,
Resetting The Keep Alive Memory (KAM) .
REPEAT the self-test.
H27 CHECK THE HO2S OUTPUT VOLTAGE
- HO2S connector disconnected.
- Visually inspect the HO2S circuit for exposed wiring, contamination, corrosion and correct assembly. Repair as necessary.
- Measure the voltage between:
( + ) HO2S Connector, Component Side ( - ) HO2S Connector, Component Side HO2S Signal SIGRTN
- Increase the engine speed to 2,000 RPM for 3 minutes.
- Carry out the KOER self-test.
- Monitor the signal voltage during the self-test.
Is the voltage greater than 0.5 volt at any time during the self-test?
Yes No GO to
H30 . INSTALL a new HO2S. REFER to the Workshop Manual Section 303-14, Electronic Engine Controls.
RESET the keep alive memory (KAM). REFER to Section 2,
Resetting The Keep Alive Memory (KAM) .
REPEAT the self-test.
H28 ATTEMPT TO RETRIEVE DTC P2195 OR P2197
- HO2S connector disconnected.
- Connect a 5 amp fused jumper wire between the following:
Point A HO2S Connector, Harness Side Point B Vehicle Battery HO2S Signal Negative terminal
- Carry out the KOER self-test.
Are DTCs P2195 or P2197 present?
Yes No GO to
H29 . GO to
H42 .
H29 HO2S VOLTAGE CHECK
- Key in OFF position.
- Remove the jumper wire(s).
- HO2S connector disconnected.
- Key ON, engine running.
- Increase the engine speed to 2,000 RPM for 30 seconds.
- Measure the voltage between:
( + ) HO2S Connector, Component Side ( - ) HO2S Connector, Component Side HO2S Signal SIGRTN
- Carry out the KOER self-test.
- Monitor the signal voltage during the self-test.
Is the voltage less than 0.4 volt at any time during the self-test?
Yes No GO to
H30 . INSTALL a new HO2S. REFER to the Workshop Manual Section 303-14, Electronic Engine Controls.
RESET the keep alive memory (KAM). REFER to Section 2,
Resetting The Keep Alive Memory (KAM) .
REPEAT the self-test.
H30 CARRY OUT A THOROUGH WIGGLE TEST ON THE HO2S HARNESS
- Key in OFF position.
- HO2S connector connected.
- Key ON, engine running.
- Engine at normal operating temperature.
- Access the PCM and monitor the HO2S Signal PID.
- Wiggle, shake, and bend small sections of the wiring harness while working from the sensor to the PCM.
While monitoring the HO2S PID, does the HO2S stop switching?
Yes No ISOLATE the concern and REPAIR as necessary.
CLEAR the DTCs. REPEAT the self-test. GO to
H31 .
H31 TEST DRIVE THE VEHICLE WHILE MONITORING THE HO2S PID FOR SWITCHING
- Access the PCM and monitor the HO2S Signal, OL and LOOP PIDs.
- Start the engine and let idle until the vehicle goes into the closed loop fuel condition.
- Drive the vehicle in a manner consistent with the freeze frame data in an attempt to simulate the original concern.
Does the HO2S PID switch?
Yes No GO to
DC28 . INSTALL a new HO2S. REFER to the Workshop Manual Section 303-14, Electronic Engine Controls.
RESET the keep alive memory (KAM). REFER to Section 2,
Resetting The Keep Alive Memory (KAM) .
REPEAT the self-test.
H32 DTCS P2270, P2272, P2271, P2273, P2274 OR P2275: HO2S LACK OF SWITCHES STUCK LEAN OR RICH
- Note: Address all continuous memory ignition and misfire DTCs before any KOER HO2S DTCs.
- Key in OFF position.
- Visually inspect for:
- pinched, shorted, and corroded wiring and pins
- oil or water contamination
- crossed sensor wires
- contaminated or damaged sensor
Is a concern present?
Yes No REPAIR as necessary.
CLEAR the DTCs. REPEAT the self-test. For KOER DTCs P2270, P2271, P2272, P2273, P2274 or P2275, GO to
H34 .
For continuous memory DTCs P2270, P2271, P2272, P2273, P2274 or P2275, GO to
H33 .
H33 CHECK FOR KOER DTCS
- Key ON, engine OFF.
- Clear the DTCs.
- Key ON, engine running.
- Run the engine at approximately 2,000 RPM. Maintain the engine speed for 3 minutes.
- Retrieve the continuous memory DTCs.
Are DTCs P2270, P2271, P2272, P2273, P2274 or P2275 present?
Yes No GO to
H34 . Unable to duplicate or identify the concern at this time.
GO to Pinpoint Test
Z .
H34 CHECK THE HO2S SIGNAL LEVEL TOO HIGH
- Note: Fuel calculations can be affected by unmetered air leaks.
- Key in OFF position.
- Carefully inspect the following areas for potential air leaks:
- hoses connecting to the mass air flow (MAF) sensor assembly
- hoses connecting to the throttle body
- intake manifold gasket leaks
- PCV system
- the vacuum lines are disconnected
- improperly seated engine oil dipstick, tube or oil fill cap
- exhaust leaks at flanges and gaskets
- With the vehicle in NEUTRAL, position it on a hoist. Refer to the Workshop Manual Section 100-02, Jacking and Lifting for the locations of the lifting points.
- Visually inspect for:
- exhaust leaks at flanges and gaskets
- HO2S not tightened to specification
- physical exhaust system concerns
- aftermarket exhaust
- punctures or cracks in the catalyst
Is a concern present?
Yes No REPAIR as necessary.
CLEAR the DTCs. REPEAT the self-test. GO to
H35 .
H35 CHECK FOR SHORTS BETWEEN CIRCUITS IN THE HO2S HARNESS
- PCM connector disconnected.
- Disconnect the HO2S harness connector.
- Measure the resistance between:
( + ) PCM Connector, Harness Side ( - ) Vehicle Battery HO2S Signal Negative terminal
- Measure the resistance between:
( + ) PCM Connector, Harness Side ( - ) PCM Connector, Harness Side HO2S Signal SIGRTN HO2S Signal VPWR HO2S Signal HO2S Heater
Are the resistances greater than 10K ohms?
Yes No GO to
H36 . REPAIR the short circuit. CLEAR the DTCs. REPEAT the self-test.
H36 CHECK THE HO2S CIRCUIT FOR AN OPEN IN THE HARNESS
- Measure the resistance between:
( + ) PCM Connector, Harness Side ( - ) HO2S Connector, Harness Side HO2S Heater HO2S Heater VPWR VPWR HO2S Signal HO2S Signal SIGRTN SIGRTN
Are the resistances less than 5 ohms?
Yes No GO to
H37 . REPAIR the open circuit. CLEAR the DTCs. REPEAT the self-test.
H37 CHECK THE HO2S CIRCUIT VOLTAGE
- PCM connector connected.
- HO2S connector connected.
- Key ON, engine running.
- Access the PCM and monitor the HO2S Signal PID.
Is the voltage greater than 1.5 V?
Yes No For partial zero emission vehicle (PZEV), GO to
H40 .
For all others, GO to
H39 . GO to
H38 .
H38 CHECK THE HO2S CIRCUIT VOLTAGE
- Key in OFF position.
- PCM connector connected.
- HO2S connector disconnected.
- Connect a 5 amp fused jumper wire between the following:
Point A HO2S Connector, Harness Side Point B HO2S Connector, Harness Side HO2S Signal VPWR
- Key ON, engine OFF.
- Access the PCM and monitor the HO2S Signal PID.
Is the voltage greater than 1.5 V?
Yes No INSTALL a new HO2S. REFER to the Workshop Manual Section 303-14, Electronic Engine Controls.
RESET the keep alive memory (KAM). REFER to Section 2,
Resetting The Keep Alive Memory (KAM) .
REPEAT the self-test. GO to
H42 .
H39 CHECK FOR OVER VOLTAGE IN THE PCM
- Key in OFF position.
- HO2S connector disconnected.
- Key ON, engine OFF.
- Measure the voltage between:
( + ) HO2S Connector, Harness Side ( - ) Vehicle Battery SIGRTN Negative terminal HO2S Signal Negative terminal
Are the voltages less than 1.5 V?
Yes No INSTALL a new HO2S. REFER to the Workshop Manual Section 303-14, Electronic Engine Controls.
RESET the keep alive memory (KAM). REFER to Section 2,
Resetting The Keep Alive Memory (KAM) .
REPEAT the self-test. GO to
H42 .
H40 CHECK THE HO2S CIRCUIT FOR A SHORT TO VPWR IN THE HARNESS
- Key in OFF position.
- PCM connector disconnected.
- HO2S connector disconnected.
- Measure the resistance between:
( + ) PCM Connector, Harness Side ( - ) HO2S Connector, Harness Side HO2S Signal VPWR
Is the resistance greater than 10K ohms?
Yes No GO to
H41 . REPAIR the short circuit. CLEAR the DTCs. REPEAT the self-test.
H41 CHECK THE HO2S CIRCUIT VOLTAGE
- PCM connector connected.
- HO2S connector disconnected.
- Connect a 5 amp fused jumper wire between the following:
Point A HO2S Connector, Harness Side Point B HO2S Connector, Harness Side HO2S Signal VPWR
- Key ON, engine running.
- Access the PCM and monitor the HO2S Signal PID.
Is the voltage greater than 1.5 V?
Yes No INSTALL a new HO2S. REFER to the Workshop Manual Section 303-14, Electronic Engine Controls.
RESET the keep alive memory (KAM). REFER to Section 2,
Resetting The Keep Alive Memory (KAM) .
REPEAT the self-test. GO to
H42 .
H42 CHECK FOR CORRECT PCM OPERATION
- Disconnect all the PCM connectors.
- Visually inspect for:
- pushed out pins
- corrosion
- Connect all the PCM connectors and make sure they seat correctly.
- Carry out the PCM self-test and verify the concern is still present.
Is the concern still present?
Yes No INSTALL a new PCM. REFER to Section 2,
Flash Electrically Erasable Programmable Read Only Memory (EEPROM) . The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.
