Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
I have posted this problem before. I finally caught this problem on my scanner and it’s one of those intermittent ones. When engine is cold below 40* the startup rpm would go as high as 2600 or 2800rpm. No codes at all no pending codes and everything looked good but I tested all cold start system’s and removed and cleaned TB. Then one morning it was 5* outside and I plugged in my Snap On scanner and there it was-40 ECT. Turned on the key and in 2 or 3 seconds it would change but was still reading low. It’s a new sensor so I grab another one do a wiggle test again then plug in the newer one and it’s the same. Scanner saying I have 5v ref but I meter it and it’s true. So I tested the yellow sig return wire for high resistance from PCM to ECT connection and it’s good. It happens so fast that it sets the idle speed but will not set a code. So PCM is going out for R&R. Has anyone else ever had this problem????? Ty all who have replied along this nightmare because this truck is mine. Ha ha
never seen this problem before,, but if you have swapped known good ect parts multiple times, and you are POSITIVE both wires going to the ecm, and connectors and pins are also good.
then it has to be a faulty ecm.
but to be sure, with the scan tool hooked up, and reading the ect pid, and you unplug the connector, it should go to -40.. does it do that??
There is a software update for the PCM specifically for this issue. Check out TSB#07-23-12
"You will always find the greatest fulfillment in life when you are operating in the gifts God gave you"- Dad
National Director of Technical Training & Mechanical Operations - Express Oil Change & Tire Engineers
ASE Master L1 Tech
BMW Master Tech
Ford FACT Advanced Electronics Instructor
TheTechWhisperer wrote: There is a software update for the PCM specifically for this issue. Check out TSB#07-23-12
that tsb is superseded by # 08-18-02. it does not state anything about coolant temp sensor failure, and talks about throttle bodies issues. is there something you know that is not posted in the tsb??
Check pin fitment at PCM harness? If that doesn't fix it then back probe the yellow wire at the PCM and ground it out. If the PCM still show -40* then it's bad.
Hey I want to say ty to all that helped with my truck. I performed all the tests and reperformed them and it’s all pointing to PCM. Ty so much for all the support
Now I have a question for you guys about luck with reman PCMs. I would love to just go to ford and buy one but that’s out of my budget. What other companies have you worked with on Ford PCMs and have had good experience.
