socket17

NO COMMUNICATION WITH PCM
2003 honda civic ex 1.7 l automatic 4 door sedan
it will only shift from 2nd & 4th
rev limited to around 3200RPM
Hard Start
Check Engine Light ON
No power / Limp Mode
No Tachometer
The check engine light is ON, the immobilizer light is flashing, there is no communication with the scan tool. The tachometer is inoperative, the temperature gauge is inoperative.
The car runs sluggishly, no acceleration, engine cuts out at higher rpm's greater than 3,400 ?

Diagnostic Steps Performed/Parts Replaced
Checked all power supplies for PCM & DLC
Checked and Cleaned All PCM & DLC Grounds
Replaced PCM with key reprogram
Removed & Inspected Instrument cluster connectors
Visually checked all ignition switch wires
Immobilizer unit




What Am I Missing here ???
everyone I've talked has never come across this.

NDNV

Loose alternator ground bolt causing PCM to fail?

socket17

[QUOTE=NDNV;50955615]Loose alternator ground bolt causing PCM to fail?[/QUOTE
I checked its tight

socket17

Update:
I have replaced the battery cause it was starting to get weak. But still the same problems. Anyone have any idea as to what could be wrong or where to go from here ?

NDNV

Still bad PCM?

Cain1977

Just to make sure your alternator is grounded I would add a ground wire 8 or 4 awg I used a 4. I added mine from a bolt on the side of the alternator and ran it to the ground wire on the chassis. I'd also pull the plug on the alternator, the plug with the 4 wires not the charging terminal and see if it will start. I had a similar issue to yours. I replaced the alternator with a new one not a re-manufactured one. Now it runs fine and all gauges work but I do have a solid battery light on. I know my old alternator was loose and it may have fried my ELD or ECU. I'm not sure so as for now I'm stuck with a battery light on. But the car does work fine.....

socket17

you were completely right !!! what I thought was a tight bolt was but stripped threads on the alternator bracket. it wasn't allowing the bolt to bottom out and ground the alternator properly and taking out the PCM .

socket17

here is the fix guys in case any one else runs into this too




What fixed the problem
A Loose Alternator bolt was causing a bad ground ay the alternator. The Bad ground was causing the alternator to over charge and short the PCM. The PCM in turn was cause the vehicle to run in a Limp mode. The Loose alternator bolt was caused by a the alternator bracket threads stripping from over-torqueing when previously serviced. Replace the PCM, alternator, and alternator bracket. Reprogramed the PCM and Immobilizer and test drove vehicle and found no further problems.