Bad harness?

I'm thinking I have a bad engine wiring harness.

Car sat for most of the last 2 1/2 years. Upon reviving it and getting back on the road I immediately had a low brake fluid warning and TCS off warning lights come on.

Well after fooling with the sensor connector, making sure the connections were good and adding dielectric grease to the connections it has become intermittent.

Next was the cam position sensor fault/check engine light on the drivers side. Swapped sensors side to side but the problem stayed on the left.

Read that this was often due to a bad alternator diode so I replaced the original, 150k mile alternator, with a new one.

That didn't fix the problem but now I have a new intermittent check charging system problem that I never had with the original alternator. Alternator is charging just fine. I'm thinking moving the wiring around during the swap messed it up.

Brake fluid was and still is fine. In fact I just upgraded to Boss brakes and did a track day at VIR Friday. They work great.

3 different potentially wiring related issues on the left side of the engine bay popping up in such a short time frame is suspect in my book.

So I'm thinking I've got a harness problem on the drivers side of the engine bay.

Anyone else experienced something similar? If so what was the culprit if not the harness?

Thanks.

What year is the car and was it stored outside?

Have you checked the smart junction box?

Car is an 07' and it was indoors about 90% of the time. When I had projects to do in the shop I would move it outside while working in the shop. Now I have more shop so it's stored indoors all the time.

Truth be told I was not privy to the smart junction box. Just started looking into this. Since I'm out of town for the next few days I'll check that when I get back. Car is running good just tired of the warnings, alarms and check engine light.

Dirtleg said:

Car is an 07' and it was indoors about 90% of the time. When I had projects to do in the shop I would move it outside while working in the shop. Now I have more shop so it's stored indoors all the time.

Truth be told I was not privy to the smart junction box. Just started looking into this. Since I'm out of town for the next few days I'll check that when I get back. Car is running good just tired of the warnings, alarms and check engine light.

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Check under the passenger side carpet for mildew. If it looks of smells like its been wet, remove the SJB from the passenger side kick panel and check for corrosion on the connectors on the back of the box.

I highly suggest obtaining the electrical diagrams in paper form for the 2007 and begin by going through and cleaning every ground connection first. You can try using the link attached but it makes use of the manual difficult when trying to locate the specific ground and splice points using the location charts. Cleaning connectors would be the next step. I would tend to avoid "dielectric grease" as it can introduce other issues when used overly generously. Best cleaning can be done with acid brushes and 90% Isopropyl Alcohol and then blow out with low pressure compressed air and allow to dry overnight. The only way to see if you have issues within the wiring harness is to begin doing continuity testing on the wiring directly relating to the systems with problems. The SJB has nothing to do with the charging system or the cam sensor issue. So I would consider that something to inspect but not a top probable cause for anything aside from the brake fluid low sensor.

With regard to the Brake fluid sensor pull the connector and check continuity across the switch. If it reads less than 2 ohms with the brake fluid full, the sensor is bad.

You've got a lot of work in front of you. Good luck.

Link to wiring diagrams for 2005 - http://iihs.net/fsm/?dir=40

redfirepearlgt said:

I highly suggest obtaining the electrical diagrams in paper form for the 2007 and begin by going through and cleaning every ground connection first. You can try using the link attached but it makes use of the manual difficult when trying to locate the specific ground and splice points using the location charts. Cleaning connectors would be the next step. I would tend to avoid "dielectric grease" as it can introduce other issues when used overly generously. Best cleaning can be done with acid brushes and 90% Isopropyl Alcohol and then blow out with low pressure compressed air and allow to dry overnight. The only way to see if you have issues within the wiring harness is to begin doing continuity testing on the wiring directly relating to the systems with problems. The SJB has nothing to do with the charging system or the cam sensor issue. So I would consider that something to inspect but not a top probable cause for anything aside from the brake fluid low sensor.

With regard to the Brake fluid sensor pull the connector and check continuity across the switch. If it reads less than 2 ohms with the brake fluid full, the sensor is bad.

You've got a lot of work in front of you. Good luck.

Link to wiring diagrams for 2005 - http://iihs.net/fsm/?dir=40

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Good advice here thanks. I've been so busy with work lately and every time I turn around the car needs something else fixed (constantly being repaired/upgraded since October) I have not had the energy to think these things through sometimes. The guidance you've presented here is much appreciated.

redfirepearlgt said:

I highly suggest obtaining the electrical diagrams in paper form for the 2007 and begin by going through and cleaning every ground connection first. You can try using the link attached but it makes use of the manual difficult when trying to locate the specific ground and splice points using the location charts. Cleaning connectors would be the next step. I would tend to avoid "dielectric grease" as it can introduce other issues when used overly generously. Best cleaning can be done with acid brushes and 90% Isopropyl Alcohol and then blow out with low pressure compressed air and allow to dry overnight. The only way to see if you have issues within the wiring harness is to begin doing continuity testing on the wiring directly relating to the systems with problems. The SJB has nothing to do with the charging system or the cam sensor issue. So I would consider that something to inspect but not a top probable cause for anything aside from the brake fluid low sensor.

With regard to the Brake fluid sensor pull the connector and check continuity across the switch. If it reads less than 2 ohms with the brake fluid full, the sensor is bad.

You've got a lot of work in front of you. Good luck.

Link to wiring diagrams for 2005 - http://iihs.net/fsm/?dir=40

Click to expand...

I was actually hoping you would chime in on this one... Nice catch on the Alt. and the SJB. Thanks!

no prob.

Haha been away for a while but got back on here recently and realized this had never been updated.

First thanks for all the help back when this was new.

Wiring harness is fine. Brake fluid switch just needed to be used regularly. I bought a new one but never installed it as the problem has gone away.

Codes for cam phaser were correct. I replaced it and no more issues.

Alternator? Well lets just say I should have never swapped out the original. The replacement is working fine but throws the charging light on occasion. Less and less it seems as I drive the car more.

Got rid of my 15' Mustang and bought a new truck so this one is seeing much more road time than it was.

Running good for the most part.

Dirtleg said:

Haha been away for a while but got back on here recently and realized this had never been updated.

First thanks for all the help back when this was new.

Wiring harness is fine. Brake fluid switch just needed to be used regularly. I bought a new one but never installed it as the problem has gone away.

Codes for cam phaser were correct. I replaced it and no more issues.

Alternator? Well lets just say I should have never swapped out the original. The replacement is working fine but throws the charging light on occasion. Less and less it seems as I drive the car more.

Got rid of my 15' Mustang and bought a new truck so this one is seeing much more road time than it was.

Running good for the most part.

Click to expand...

Just because its new does not mean it is working right. First off 99% of the replacement alternators for our cars are rebuilt because they are of an archaic design and nobody actually makes them anymore. I had Ford put a new alternator for me under warranty and the brand new one was bad and the car sat an extra day waiting for another replacement. I've went through 4 alternators in a short period of time until I switched to a fifth one which is 2010 alternator. Haven't had an issue for years. So just saying, it still might be an alternator issue.