The manual also had these diagrams:




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Bingo! Sorry for long reply been busy up here at work between shop work and alingments

 

Common bump bump

 

Did you check the resistance of the VMV as Bill mentioned before?

 

This thread is a couple of months old, but I am going to revive it since I have the same problem with my '96 F-150 5.8. CEL, flashing TCIL, codes P0443 and P0713. The transmission has definitely not been overheated; I bought it with a bad tranny and have had a gauge on it since day 1 with the replacement. I would not have thought these two were related, if not for this thread and this other one; after finding these, I unplugged the VMV and sure enough, the TCIL stops flashing.

I tested the VMV tonight; 32 ohms across the pins. I have battery voltage at the harness red wire with the key on. I have not yet tested the wire to the PCM but that is my next step.

Assuming there is not an open in the circuit to the PCM, any ideas?

 

I did a little more investigating tonight; in addition to having power on the red wire, I have continuity on the green/black wire between the VMV connector and PCM pin 56. So the circuit seems OK; the VMV itself tests about 32 ohms across the pins.

Any suggestions? I am leaning more and more toward the PCM itself being the problem, but don't want to jump to conclusions.

 

The other thread showed one response where a new PCM fixed the issue. I am not sure if the poster had the same exact symptoms.

We did ask the OP to try disconnecting a different sensor to see if the symptoms changed. I am not sure if they ever tried that. The theory was another sensor was pulling down the VREF signal, the P0443 error was just another symptom not the root cause.

 

I had seen that post as well; I'm just trying to make sure I cover my bases before trying a different PCM.

I did see a post in the other thread where the OP disconnected a number of other sensors that you mentioned were in the same harness; regardless of what other sensors he unplugged, he got the same TCIL behavior relative to unplugging/plugging in the VMV connector.

I have not checked continuity to ground on the green/black wire under different conditions, as mentioned in this post, so I will try that tonight.

Besides P0443 and P0713, I also have a code (P1409) for a fault in the EGR vacuum solenoid circuit. Diagnostic results for the EVR circuit are about the same as the VMV circuit - power on the supply wire, continuity to the PCM on the return wire, appropriate resistance across the solenoid. I don't want to muddy the waters too much, but it seems like these could be two different manifestations of the same issue. What do you think?

 

My EVTMs are not close by ATM, I cannot verify if the EVR supply voltage is the same as the VMV. Regardless I would verify the supply voltage for the VMV is staying within range before going for a new PCM. A few minutes of rigging in a DVM then going for a drive would confirm or debunk my VREF theory.

 

I will give that a shot tonight and report back. Thanks for the suggestion.

 

The green/black wire seems to provide a path to ground any time it is connected to the PCM, key/engine on or off. It does not provide a path to ground when the PCM is disconnected, so I don't think I have a short in the wire.

Same story on the EVR circuit: supply wire is hot with key on; return wire provides a path to ground any time the PCM is hooked up, key/engine on or off.

I spliced into the red supply wire for the VMV and ran a wire into the cab to hook up my DVOM; driving around with the meter on I never saw it drop below 14V.

What else can I check?

 

I posted about this issue and my diagnosis so far in an old thread I had going about my P0713 code; someone over there said they had solved this problem on more than one truck by replacing the PCM. I have one coming from a salvage yard; I will post back if it solves my problem.

Thanks for the help.

 

Did you clear the codes before you drove the truck again? Did the Check Engine Light come on when you were driving?

 

I cleared the codes before I drove the truck; the CEL came back almost immediately with the same codes for EVR and VMV (not sure about the P0713 since my scanner does not read transmission codes).

 

I guess my Supply Voltage theory is busted.....