Electrical Problem - Help Needed

Stangphan

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Long Post Incoming...

I am having a bigtime electrical issue that I am hoping I can get some answers/help with. I have used the search bar and read through countless threads describing similar problems, but nobody seems to know or post the actual fix. The threads all fizzle out. I will be as detailed as I can with what changes I have made and what troubleshooting I have done.

I have a 2005 Mustang GT. I am running AM cat-backs, JLT series 3 intake, and bama tune. I previously had an offroad X-pipe on it, but got tired of the codes from not getting it tuned, so I went back with the stock H-pipe. About 3 months prior to going back to the stock H pipe, my AC stopped working and the car started throwing other codes. It began throwing P0443 (EVAP Circuit) and P0645 (AC Clutch Relay Circuit).

I have checked and confirmed that all of my fuses and relays are good.

I changed the purge valve and no change happened. Then I started to troubleshoot the AC. Sometimes the AC works, but most time it does not. It is not low on freon. I checked for power at the fuse box and was getting all power but the ground that the PCM is supposed to send to engage the AC clutch was not there. I could jump the pins and the compressor would run all day. I then went to the clutch cycling switch and jumped the pins and the compressor would run all day. I changed the cycling switch and have not had the AC code since, but still do not have AC.

The next day I was on the interstate and the car just quit...showed the wrench light, lost power, drove to the off-ramp, and it cut off. I ran the codes and got the following: P2105, P151A, P0645, P0600, P0481, P0480, and P0446. Started it back up and had no problems. The next day I took the fuse box completely apart and crimped down each wire connector in the bottom of the fuse box to ensure there was a good connection. I reset the codes and haven't had that problem since.

Now I am getting codes P0135, P0141, P0155, P0161, and P0443.

I am wondering if I have a PCM problem, my tune screwed it up, or something else...just can't seem to figure it out but the problem seems semi-common. Any help? Will cross-post on a couple other places.
 

DieHarder

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Long Post Incoming...

I am having a bigtime electrical issue that I am hoping I can get some answers/help with. I have used the search bar and read through countless threads describing similar problems, but nobody seems to know or post the actual fix. The threads all fizzle out. I will be as detailed as I can with what changes I have made and what troubleshooting I have done.

I have a 2005 Mustang GT. I am running AM cat-backs, JLT series 3 intake, and bama tune. I previously had an offroad X-pipe on it, but got tired of the codes from not getting it tuned, so I went back with the stock H-pipe. About 3 months prior to going back to the stock H pipe, my AC stopped working and the car started throwing other codes. It began throwing P0443 (EVAP Circuit) and P0645 (AC Clutch Relay Circuit).

I have checked and confirmed that all of my fuses and relays are good.

I changed the purge valve and no change happened. Then I started to troubleshoot the AC. Sometimes the AC works, but most time it does not. It is not low on freon. I checked for power at the fuse box and was getting all power but the ground that the PCM is supposed to send to engage the AC clutch was not there. I could jump the pins and the compressor would run all day. I then went to the clutch cycling switch and jumped the pins and the compressor would run all day. I changed the cycling switch and have not had the AC code since, but still do not have AC.

The next day I was on the interstate and the car just quit...showed the wrench light, lost power, drove to the off-ramp, and it cut off. I ran the codes and got the following: P2105, P151A, P0645, P0600, P0481, P0480, and P0446. Started it back up and had no problems. The next day I took the fuse box completely apart and crimped down each wire connector in the bottom of the fuse box to ensure there was a good connection. I reset the codes and haven't had that problem since.

Now I am getting codes P0135, P0141, P0155, P0161, and P0443.

I am wondering if I have a PCM problem, my tune screwed it up, or something else...just can't seem to figure it out but the problem seems semi-common. Any help? Will cross-post on a couple other places.

Grounds, tune, connectors/wiring age/corrosion/shorts/opens all are common issues. You mentioned working on the fuse box cleared up your issues for a time, then new problems showed up. Might be beneficial to trace the wiring for the current codes to identify any commonalities and check/clean/ test/ confirm continuity of grounds/wiring/connectors and modules. Keep a log. Start w/current issues and determine what they have in common (i.e. current codes are 02 heater circuits and the last is the EVAP).

I often find that age/corrosion/connectors/connector pins; grounds/wiring; and modules (rare) can fail but primarily active components or things I've messed with (most often).

If you can determine whether the affected components narrow down to something in common, like a connector/wiring bundle/splice and/or grounds you might try removing them/check for any dirt/corrosion; check for damaged wiring/pins/pin height/check for continuity; clean as needed and reconnect/reseat; clear codes and retest for results.

A quick check of your system (Wiring manual Pg 24-4) shows that all of the circuits in question appear to have connector C175E in common which connects to the PCM and the other side is a splice S101 which then runs to Pg 24-2 out at E and into the BEC (PCM Pwr Relay) at C1035B. The EVAP Purge valve also on C175E runs to Pg 24-2 out at D and into the BEC (PCM Pwr Relay) at C1035A. Those lines service Fuse 47.

See circuits below.

Pg 24-4
https://iihs.net/fsm/?d=40&f=Electronic Engine Controls - 4.6L.pdf&p=4
Pg 24-2
https://iihs.net/fsm/?d=40&f=Electronic Engine Controls - 4.6L.pdf&p=2
Pg 24-5
https://iihs.net/fsm/?d=40&f=Electronic Engine Controls - 4.6L.pdf&p=5

If I were troubleshooting I would start with what you touched last which was the BEC (check your work/also check 1035A & B); check/clean/ensure tight fit of the blocks (Some people like dielectric grease; use at your discretion); Retest. If no change then I'd move onto C175E (remove, check, clean), then test continuity (point-to-point ohms check) from C175E to C1035 A & B. After that you'd have to look at splice S101 but the fact that all of the codes have C175E in common I would concentrate on that and the BEC.

Personally, I've had the most issues w/grounds to the point where I added a 4 gauge cable from a mounting bolt on the alternator back to the main ground on the passenger strut tower. Once I did that all of my ground related issues (gas gauge/charging/relays/fan problems/etc.) cleared up. I did also have a PCM ground output (for the engine fan) fail once. Asked Lito for a tune to turn the fan on at 40 deg which worked for testing so that eliminated equip/wiring/relays and PCM. Ended up reloading the tune (with normal fan temps) and the problem disappeared.

Hope this helps.
 
Last edited:

Stangphan

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Grounds, tune, connectors/wiring age/corrosion/shorts/opens all are common issues. You mentioned working on the fuse box cleared up your issues for a time, then new problems showed up. Might be beneficial to trace the wiring for the current codes to identify any commonalities and check/clean/ test/ confirm continuity of grounds/wiring/connectors and modules. Keep a log. Start w/current issues and determine what they have in common (i.e. current codes are 02 heater circuits and the last is the EVAP).

I often find that age/corrosion/connectors/connector pins; grounds/wiring; and modules (rare) can fail but primarily active components or things I've messed with (most often).

Personally, I've had the most issues w/grounds to the point where I added a 4 gauge cable from a mounting bolt on the alternator back to the main ground on the passenger strut tower. Once I did that all of my ground related issues (gas gauge/charging/relays/fan problems/etc.) cleared up. I did also have a PCM ground output (for the engine fan) fail once. Asked Lito for a tune to turn the fan on at 40 deg which worked for testing so that eliminated equip/wiring/relays and PCM. Ended up reloading the tune (with normal fan temps) and the problem disappeared.

If you can determine whether the affected components narrow down to something in common, like a connector/wiring bundle/splice and/or grounds you might try removing them/check for any dirt/corrosion; check for damaged pins/ pin height/check for continuity; clean as needed and reconnect/reseat; clear codes and retest for results.

A quick check of your system (Wiring manual Pg 24-4) shows that all of the circuits in question appear to have connector C175E in common which connects to the PCM and the other side is a splice S101 which then runs to Pg 24-2 out at E and into the BEC (PCM Pwr Relay) at C1035B. The EVAP Purge valve also on C175E runs to Pg 24-2 out at D and into the BEC (PCM Pwr Relay) at C1035A. Those lines service Fuse 47 and the PCM Diode so ensure those are good.

See circuits below.

Pg 24-4
https://iihs.net/fsm/?d=40&f=Electronic Engine Controls - 4.6L.pdf&p=4
Pg 24-2
https://iihs.net/fsm/?d=40&f=Electronic Engine Controls - 4.6L.pdf&p=2
Pg 24-5
https://iihs.net/fsm/?d=40&f=Electronic Engine Controls - 4.6L.pdf&p=5

If I were troubleshooting I would start with what you touched last which was the BEC (check your work/also check 1035A & B); check/clean/ensure tight fit of the blocks (Some people like dielectric grease; use at your discretion); Retest. If no change then I'd move onto C175E (remove, check, clean), then test continuity (point-to-point ohms check) from C175E to C1035 A & B. After that you'd have to look at splice S101 but the fact that all of the codes have C175E in common I would concentrate on that and the BEC.

Hope this helps.


This is so helpful. I appreciate the detailed response! I will try to begin diagnosing some of those tonight/this week!
 

07 Boss

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I went through 4 or 5 alternators before I switched to a 2010 one and have had zero issues since. I think I still have a new, not remanufactured, alternator for 2005-2009 on the shelf somewhere that I never used because I switched. I just always kept it around in case but I have never needed it since switching.
 

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