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Lying PCM

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Some weeks ago I was working on a 2001 F550 7.3L that had a bad PCM - no communication with the module. After the new PCM was installed and it got the 8 injectors it needed I road tested the truck. Near the end of my road test the engine started emitting heavy black smoke, the idle was high around 1200 RPM and the sucker had gobs of power.

 

It had no DTC's!

 

Knowing what I know, I suspected an ICP or IPR problem.... but then again, I did install 8 reman injectors. I unplugged the ICP and the engine settled down. I reconnected the ICP, checked some PID's and the ICP voltage was 0.24V KOEO. KOER the idle was high and erratic, LOAD = 0% and the IPR was in the 20% range if I recall correctly.

 

I pulled the IPR to look at the seals, spun in a known good one - no change which I expected. I looked at the ICP sensor, spun in a known good one - no change. I was hoping for one of those "in-range" biased sensors. No luck.

 

On goes the Break Out Box and I performed the circuit tests for the ICP sensor and the IPR - no problem found. Since I had the BOB hooked up I decided to strart looking at some voltages. Low and behold the ICP voltage at the BOB was 1.8V and the IDS was showing 0.85V at idle. I Service Installed the PCM and the problem was corrected.

 

Just another tale thought I would share. Posted Image

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