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[PDK1953]

Anyone help please
Last year I had problems with my 1999 2.2 CDXi petrol auto estate ... The Auto gearbox warning light kept coming on and putting gearbox in to "limp home" mode. After many hours on this forum and trying lots of suggested options (thanks again for all the help) including a thorough check of the gearbox itself, I appeared to trace the fault to the throttle potentiometer in the driver footwell ........... fitted a new one and bingo problem solved ................ or so I thought !!! It has recently started displaying the same annoying symptoms again, but this time more intermittently and now accompanied by no throttle response when depressing the throttle pedal ? The error codes are suggesting the throttle body is not responding. So today I fitted a clean refurbished throttle body (using the maintenance guide section of this forum .... first class instructions, worked a dream) . Turned the key and it started first time with instant throttle response. Sorted !!!?? Ran the engine for 10 minutes still working fine so switched off and put the tools away. Went back 15 minutes later turned the key and it started first time ......... but this time the dreaded service warning light on the dash (outline of car with a spanner) stayed on and yes you've guessed no throttle response, car happily ticking over on idle but would not respond to throttle pedal. So turned it off (cursing to myself under my breath) and tried again .... same problem. Turned it off again, but this time I took the key fully out of the ignition switch, (a trick someone suggested last time) put it back in, put my foot gently on the throttle pedal and turned the key praying at the same time ........ and as if by magic the service light went out and the throttle was working ? Having replaced both the throttle potentiometer and the throttle body can anyone please shed some light on to the potential cause of my problem I am convinced the gearbox is ok and only switches into "limp home" mode because the ECU cannot workout what the real problem as the road speed sensors and throttle sensors are giving it confusing information, or am I just living in hope ? Any help please.

[davethediver]

Sounds like a possible CAM sensor issue to me?

Would suggest getting the codes read, as the lights you have talked about aren't autobox or service lights.

Problems seem very similar as to what i had a few years ago, if it does turn out to be the CAM sensor remember its a main dealer genuine VX part only no pattern shite or it will fail again 

[PDK1953]

Thanks for quick response, 
CAM sensor was suggested last time and so was replaced using a genuine GM part, unfortunately it made no difference 
Sorry for any confusion caused by my description of dashboard warnings, the light that stays on is the EML (car with spanner through it) the automatic gearbox warning is showing on the digital  display screen.
Hoping to get codes read at local main dealer later this week. He has suggested an ECU update might help ? worth doing or is this a money spinner for him ?

[Kevin Wood]

It does sound like a problem with the DBW throttle system. The other major component of this is the throttle body, of course. It's not impossible that there's some intermittent wiring between them that's causing it to drop into limp home.

I would get the engine codes read. These should identify which part of the system it's not happy with.

[PDK1953]

I had the fault codes read today by my local VX main dealer, There are lots of them but all seem to me to be related ??

So help from the techie guys please, please, please :-

ENGINE : In order as displayed :-
P0120NP - Throttle position sensor 1-2 correlation
P0220NP - Throttle position sensor 1-2 correlation
P1526NP - Trottle position, no adaption
P1550NP - Electronic Throttle Control Management
P1555NP - Throttle Position Sensor (TPS) load signal not plausible with engine load ***THIS TO ME, BEING AN UNTRAINED MECHANIC, IS I THINK THE ROOT CAUSE OF MY PROBLEMS AND WHY THE AUTO GEARBOX WARNING IS DISPLAYED ***
P1500NP - Electronic Throttle Control Motor Failure
P1525NP - LIMP HOME position error
P0100NP - Mass Volume Air Flow Circuit Low Input
P0170NP - Rich exhaust

TRANSMISSION
P0706NP - Automatic Transmission Range sensor circuit, Range/Performance
P1890NP - CAN receives error
P1781NP - CAN receives error
P0748NP - Pressure Control solenoid circuit high input
P1740NP - Torque Control Failure detected by Engine Control Module

All Codes have now been cleared and I was advised that the ECU's did not require updating.

My local dealer did suggest that clearing the codes using the proper VX software this time "may" be more beneficial than using the universal code reader system that had been used previously. He also suggested that the throttle system failures may be giving rise to the transmission fault codes if the engine loads and drive loads are inconsistent ....... something I have thought for a long time but has always been dismissed by previous mechanics  .... I would seriously welcome any other thoughts that anyone may have ............... this saga is driving me slowly insane !!!

Car is now driving as smoothly and effortlessly as it did when I bought it 5 years ago, the only difference is I'm driving it with my fingers crossed all the time.

So to recap I have :
Replaced CAM sensor with new genuine VX part , Replaced Mass Air Flow Unit with new genuine VX part, Replaced Throttle Potentiometer and Throttle Body Unit with verified recycled parts and new genuine VX gasket (both recycled parts are from same donor vehicle and both known to be working prior to transfer) Cleared all Fault Codes. When replacing the Throttle Body on Monday I also noticed that the join between the Mass Air Flow Unit and the Air Intake Pipe from the Throttle Body was loose and allowing air to be drawn in to the pipe post Air Flow Unit, this has now been secured and sealed using a new screw clip.

In light of the knowledge of the above fault codes I would now ask for any feedback please.

[Kevin Wood]

Well, the codes all point towards a problem in the throttle body. Could also be the wiring between it and the ECU, of course. Do you still have the old one? Worth swapping back in case the new unit was faulty?

Gearbox ECU will rely on a load signal from the engine ECU via CAN and this comes from the throttle position sensor, so the gearbox codes, and the other engine codes, may well be related, and I wouldn't worry about them unless they persist after the engine issue is fixed.

[PDK1953]

Thanks for feedback, 
Nice to know my logic is taking me in the right direction ......... the old throttle body was not looking good when I removed it on Monday, the butterfly itself was quite stiff to move and has a thick brown deposit on both sides and the body itself was covered in oil which appeared to be coming from the air intake pipe via the large oil breather pipe from the air intake to the "ohc cover", or in my day the "rocker cover!!" .. The smaller oil breather pipe from the ohc cover to the base of the throttle body was also blocked and had perished inside!! This has now been replaced with a nice new pipe 
The majority of these fault codes, bar probably one, would have been from the removed throttle body. I do however intend to attack it with Carb Cleaner and WD40 and see if I can refurbish it to its former glory .......... not sure how to test it after I've cleaned it though ?..... If I connect it to the DBW plug and switch on the ignition and depress the throttle will the butterfly move or does all the DBW electrics only work when the engine is running

Again thanks for your thoughts

[Ken T]

I remember when I was doing a cambelt, and forgot to plug in the connector to the throttle body, I got the same fault symptoms, no throttle response and a warning light. As Kevin said, the wiring from the throttle body to the ecu maybe worth a check.

Ken

[Kevin Wood]

If the old throttle body was only causing problems through being dirty and sticking, might be worth giving it a good clean with carb cleaner and see if it's any better.