after write entire no more tach signal 07 Vette

[ccrp]

I am fighting with a weird issue on a 07 E38 PCM. After I did a write entire when new PCM was swapped into car I can not get any tach outputs anymore. HUD and instrument panel won't show a thing, all other gauges are working fine.

Tach does the self check thing with ignition on but doesn't show revs when engine is running, I can see revs via OBD2 connector on laptop though.

what can I do, I tried various write calibrations, write entires, check settings with other similar cars but can't find anything worng.

any ideas?

Tach type is set to "crank" and factors are 15/15 as stock

[[email protected]]

You mentioned that you had to put a new PCM into the car, what happened to cause that? When the new PCM was installed, was it also relearned to the other modules? Do you have any other codes or problems with it?

Bob

[ccrp]

The Vette hit a pole at slow speed exactly between the passenger side front wheel and door, exactly where the PCM sits. PCM got split in half and needed replacement.

New PCM has been reflashed with old programm, wiring harness has been repaired with new pig tails from EFIconnection and checked. Engine runs, no codes, all up and running as it should. Except no tach signal. It has been relearned to other modules, only the airbag modules needs to be changed but at the moment GM doesn not deliver any spare parts to Europe anymore as there European distributor Kroyman went belly up.

[Chris@HPTuners]

maybe you need to connect a scope to the tach output and see if it has a signal there. The output is enabled whenever the Tach Type is set to Freq or Crank. It is disabled if the type is set to serial.

[ccrp]

did that and no signal comes out of PCM. It is set to crank and not serial like it should be for 2007

[Chris@HPTuners]

when the ECM was first replaced did the tach work? Did a dealer replace the ECM?

[ccrp]

i replaced the pcm and i also reflashed the pcm wit old performance tune. tach worked, but no more after the first write entire

[Chris@HPTuners]

so just to be clear:

1. you got a new PCM that was setup by a dealer (tach was working)
2. you flashed it with a tune, write cal only (tach still working)
3. you did a write entire then tach stopped working.

can you send me or post the file you wrote to the PCM cal only when the tach still worked, and also the file you wrote to the PCM on the write entire.

I can't think of any reason this would cause a problem. A write entire using our software is the same as a flash the dealer performs.

[ccrp]

CHris, this is correct, I got a PCM from sparePCM which had the correct stock tune on it with correct VIN. I installed it and engine was running poorly (due to mods on engine) but tach was working. I copied over the old old performance tune and did a write calibration, tach was still working and engine running well like it did before accident.

Then I saw that TCS patches were not enabled and wanted to disable VATS which requires a write entire, so I did a write entire with same tune - tach stopped working, engine still running well.


I have also tried to do a write entire with the stock programm like it was shipped to me to see if it works, again, no tach

I'll post the tune a bit later, it is on my workshop laptop

[Chris@HPTuners]

well i really can't explain why this would happen, please post the file. The fact that you write entire with the original file and still no tach makes me think something has failed in the PCM. About all i can think of is to disconnect the battery for a couple of mins then reconnect and see if something comes good.

[[email protected]]

I would agree, I was thinking the PCM could be the problem, doesn't really sound like anything else.