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[JamesV6CDX]

My non-functioning rear multiram is getting harder to diagnose! I am almost fresh out of ideas now.

So far, have checked the following:

1) There is definately a good vaccum

2) Vacc tank one way valve IS working

3) Tech2 is able to actuate both rams with the engine off, so it's also obviously storing a good vaccum! And the fact that Tech2 can actuate it, means the wiring from the ECU is ok, and the actuator is OK

Yet I still cannot get the multiram to work, by blipping the engine. I've tried revving it hard, soft, midrange etc, it just will not function (I tried a different V6, which worked straight away).

I would really appreciate ideas, it's obviously not having an enormous effect on the car, it's still drivable, but I WOULD like to get the kick of the rear multiram!!

[Dave-C]

Stab in the dark, is your TPS OK?  

[JamesV6CDX]

Stab in the dark, is your TPS OK?  

No fault codes, or anything that would lead me to believe otherwise.
Is the Throttle position sensor related to the multiram in any way?

[Kevin Wood]

TPS could be one of the inputs that the ECU uses to determine when to open it. I'd expect fault codes or at least poor running if it were faulty though.

 :-/

ECU is clearly not commanding it to open. We have proven it can if it wants to. I would say that either there's an input to the ECU that's preventing the multiram working or the firmware is slightly different in this ECU to the other one you tried and it doesn't open it on a quick blip.

Since there's no fault code I'd try a look at the live data and see if it's plausible. Things like a faulty coolant temperature reading might cause it (maybe ECU disables the multiram during warmup?) Also, why not try connecting up some means of indication in the car (vacuum gauge plumbed into actuator or light bulb across solenoid feed) and see if it actually works during normal driving?

Kevin