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Author Topic:  Suspected bad ECM, questions  (Read 279 times)

Offline guitar333

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Suspected bad ECM, questions
« on: September 19, 2021, 04:36:11 PM »
Hey guys,

Long story short I replaced my fuel injectors and cooling fan recently.
Car ran fine for about 10 miles and started to act up after that.

Car runs terrible and has the codes :

P0642 (5V Sensor Reference Circuit Low)
P0236 (Turbo Boost Sensor Circuit Range)
P0193 (Fuel Rail Pressure Sensor Circuit High)

Those sensors share the same 5V reference circuit from the PCM and the circuit is only reading .5V with all the sensors unplugged.
The wiring harness continuity tested fine with ECM unplugged. I’ve come to the conclusion that I need a new ECU.


Do you agree with the above and if so, can I reprogram the replacement ECU myself with FORScan? What about the keys? Also, will my Livernois X3 tune download after the swap?
« Last Edit: September 19, 2021, 06:48:24 PM by guitar333 »
2010 SHO - CAI, Downpipes, CR Rebuilt Turbos, LMS SIII Tune, H&R

1990 SHO - 3.2 Supercharged, all the modz

Offline LMKS012

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Re: Suspected bad ECM, questions
« Reply #1 on: September 19, 2021, 08:27:47 PM »
If the car ran fine for 10 miles I would suspect a short somewhere before the PCM just "went bad".

I would also check all the fuses.  Could easily be a fuse popped because of a short.

Offline guitar333

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Re: Suspected bad ECM, questions
« Reply #2 on: September 20, 2021, 07:12:45 AM »
That’s what I thought but there is no fuse on that circuit. I can’t find a shirt with the ECU unplugged, everything checks out. I have an ECU on the way I just want to confirm it I can program my VIN
2010 SHO - CAI, Downpipes, CR Rebuilt Turbos, LMS SIII Tune, H&R

1990 SHO - 3.2 Supercharged, all the modz

Offline LMKS012

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Re: Suspected bad ECM, questions
« Reply #3 on: September 20, 2021, 01:41:19 PM »
Then pull the PCM, backprobe the connection for that circuit and check for continuity to ground.

If it is grounded then you know you have a short. 

Then go back through everything you did (ie, undo the intake, and the new cooling fan, ie, remove them) and check to see where you pinched a wire somewhere.  You probably pinched a harness and two wires within the harness are shorting, that is why you physically remove everything you bolted down prior, since a bolted flange somewhere is most likely where you pinched a harness, so watch carefully as you unbolt things to see where it is pinched.

Sucks, yeah, but no big deal really and the only way to fix this issue.

 


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