Ignition does not shut off truck after EBL Flash II install

[Wolvrine82]

You need to ask BobR (or RBob depending on what site you're on) if your 1227747 modified ECM is interchangable with a 1228747. Then fix the code 51.

The code 51 has only appeared with the 1227747 ecm with the calpack and prom. I do not have the code 51 with the EBL ecm or with the 1228747 ecm.

 

[Wolvrine82]

ust as a side thought, when you added the 3 wires to your harness for the cable to connect up to a laptop, did you double check they went into correct positions? I can't say that would cause this problem, but if it is the only change made besides the ECU it could have an effect.

Yes, that was one of the first things I verified. Even had my son double check me - old eyes you know.

 

[Wolvrine82]

Is there any chance the th400 is not the stock trans? Did the previous owner change the chip to accommodate the th400 and not change the ecm?

According to the RPO codes, the truck came with the TH400.

 

[PlayingWithTBI]

switched on the left turn signal - it blinked twice and the truck died. I initially thought it was because of the low idle. Restarted the truck and switched off the ignition and the truck shut off normally. I've started it probably twenty times since with normal operation of the ignition switch.

Wow - PFM!

 

[JDGMC]

Update on the EBL Flash ecm. I went out and started the truck like normal. Switched the ignition off and removed the key with the engine still happily running. I checked the radio - not powered up, checked the heater controls - not powered up, switched on the left turn signal - it blinked twice and the truck died. I initially thought it was because of the low idle. Restarted the truck and switched off the ignition and the truck shut off normally. I've started it probably twenty times since with normal operation of the ignition switch.
I swung by our local salvage yard and they had a 1228747 ecm. I swapped my prom and calpack over and installed it into the truck. Truck starts and runs normally - well normally for it (the idle has been messed with and it has a miss going on) with no ses light. Swapped the EBL ecm back in and still starting and shutting down normally.
I did not get a chance to check for power at the EBL ignition pin or pull the ignition fuse prior to it fixing itself with the turn signal application. So, for now, I will continue on with the EBL ecm and update this thread with any future occurences. Thank you everyone for your kind assistance.

Glad it's behaving. You're getting close to the real culprit. Using the acc strategy helps with honing in on a particular circuit. I wish these things fix themselves, but not likely. If and when it happens again you know where to start and continue on to wiring and grounds/shorts. We'll be here.

 

[Scooterwrench]

Update on the EBL Flash ecm. I went out and started the truck like normal. Switched the ignition off and removed the key with the engine still happily running. I checked the radio - not powered up, checked the heater controls - not powered up, switched on the left turn signal - it blinked twice and the truck died.

This is a stretch but the turn signal and hazard lights are on the same switch but the turn signals are a keyed circuit and the hazards are on a constant battery circuit. Makes me wonder if something in the turn signal switch has gotten crossed with the hazards and feeding batt. voltage back through turn signal switch and back into the key on circuit in the ign. switch. Might explain the two turn flashes killing the engine. Doesn't explain the thing acting right with the factory ECM installed though. Only other thing came to mind is the alternator feeding back through the charge indicator wire and back into the key on circuit and the turn signal loaded it enough to drop the voltage and shut down the ECM,again that's a stretch.

 

[Road Trip]

This is a stretch but the turn signal and hazard lights are on the same switch but the turn signals are a keyed circuit and the hazards are on a constant battery circuit. Makes me wonder if something in the turn signal switch has gotten crossed with the hazards and feeding batt. voltage back through turn signal switch and back into the key on circuit in the ign. switch. Might explain the two turn flashes killing the engine. Doesn't explain the thing acting right with the factory ECM installed though. Only other thing came to mind is the alternator feeding back through the charge indicator wire and back into the key on circuit and the turn signal loaded it enough to drop the voltage and shut down the ECM,again that's a stretch.

From reading through this thread I think that we're all converging onto a similar theory. The silver lining
to the OP's cloud is that these are the kinds of strange problems where we all end up learning so much more
about how these older systems can break...as long as we remain vigilant & keep the comm lines up.

Like @JDGMC said, "We'll be here."

 

[shawnmichael]

Im curious, have you noticed if headlights are consistently on/off with the problem? I've got the same issue right now, no tune and no changes other than replacing the dimmer switch under the column. My issue occurs only when headlights are on. Truck will not turn off until switch is turned off. I checked wiring of pigtail and all looks good so I've convinced myself it's my 31yo ignition switch but will find out soon when I replace it?!?