Check engine light
Thread Starter
Racer
Joined: Apr 2006
Posts: 405
Likes: 1
From: Twinsburg OH
Check engine light
The only trouble code I get is C15 on the ECM (coolant temp low). The temp does act strange sometimes. It reads normal for a while then goes low bounces around a bit then goes back to being accurate for a while. The analog gauge stays rock solid at normal during this.
What is bothering me more right now though is according to the C4 guru code reading sheet I have there should be a C12 code in all 3 modules and I am only getting one for module 1 (CCM).
Any help on this would be great.
What is bothering me more right now though is according to the C4 guru code reading sheet I have there should be a C12 code in all 3 modules and I am only getting one for module 1 (CCM).
Any help on this would be great.
Drifting
Joined: Aug 2006
Posts: 1,326
Likes: 18
From: Los Angeles California
I had the exact same problem in my '96 and it made the engine management go absolutely nuts when the temp reading would fluctuate, like bucking hard and stalling. It's bad. Since it's intermittent, you have some wiring or a connector that's loose, of course.
What I did to track it down was unplug the PCM connectors, use the FSM to figure out which pins were what, and then I stuck a multimeter in the two pins of the connector that belonged to the CTS wires so that I could check continuity of the entire circuit. After wiggling all the wiring around and messing around with the connector I found that the circuit went wide open when the connector was on normally, and only occasionally made contact when things vibrated and the connector backed off a little. That occasional contact made things go crazy. Replacing the $10 wiring pigtail fixed everything.
What I did to track it down was unplug the PCM connectors, use the FSM to figure out which pins were what, and then I stuck a multimeter in the two pins of the connector that belonged to the CTS wires so that I could check continuity of the entire circuit. After wiggling all the wiring around and messing around with the connector I found that the circuit went wide open when the connector was on normally, and only occasionally made contact when things vibrated and the connector backed off a little. That occasional contact made things go crazy. Replacing the $10 wiring pigtail fixed everything.
Thread Starter
Racer
Joined: Apr 2006
Posts: 405
Likes: 1
From: Twinsburg OH
Thanks for the response, I thought it was in the wiring too but was wrong. I was lucky enough to have it fail completely right after I posted and had the neighbor watch the dash while I poked the sensor with a long screwdriver, the sensor not the connector or wiring. She said it started reading correct when I was poking it. After removing the sensor I saw some kind of sealant on the threads and where there was none there was corrosion. After putting in a new sensor, I had picked one up for $12 just in case, all is good and running great again. By the way on my car anyway an open ground reads a solid 142 degrees no matter what temperature the motor is at.
I am still wandering about not having a C12 code on the ECM or the EBCM. Could someone in the know let me know if it should only be on the CCM or should I have it in all 3 places?
Thanks.
I am still wandering about not having a C12 code on the ECM or the EBCM. Could someone in the know let me know if it should only be on the CCM or should I have it in all 3 places?
Thanks.
Instructor
Joined: Jul 2004
Posts: 210
Likes: 0
From: Lakewood CO
I don't have a good answer for you but when my connector was loose I experienced the exact same thing with my '92. I got a C15 in the CCM but no other codes.
Dave
Thread Starter
Racer
Joined: Apr 2006
Posts: 405
Likes: 1
From: Twinsburg OH
By the way I never had any other symptoms it ran great pulled hard, I am hoping to get a bit more than 16MPG but probably won’t tell my foot gets about 20LBS lighter.
