4L60E auto lunges forward on cold starts

[Immortality]

This might be worth a read.

Engine diagnostic code 28

Hi all, My VR has thrown the engine check light a few times over the last week. Upon pulling codes this morning I only got #28. (had several at the start of the week, but cleared them) My manual says "transmission error - consult a specialist" but so do several other fault codes. So I figure...

forums.justcommodores.com.au

After cleaning mine the transmission was smoother.

Did a trans service today on the Calais. Also pulled out the pressure manifold to inspect and clean. Glad I did. The fluid in the pan is well used but not totally dead or burnt but there is still a huge amount of crap in the switches on the manifold. It's hard to see in the pic but it's all grey, almost like fine wear particles of alloy.
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Also took the time to fit a .490 reverse boost valve upgrade and alloy deep pan for good measure.

I'm not 100% sure how this works but from what I can see, when the PCM selects a gear it activates the appropriate solenoid which then pressurises the relevant circuit, somewhere at the end of that circuit is this manifold switch that once the circuit is pressurised switches the relevant switch on the manifold and that tells the PCM the gear change has happened. It would seem that the manifold circuit point is a dead end so any contaminants in the fluid have no-where left to go but accumulate on the switch faces.