Most of the time my '02 VDP drives perfectly and shifts very smooth (difficult to even identify the shift points) but at random it will drop to limp home mode / restricted performance and says Gearbox Failure on the dash with both amber and red lights. The code is P1122 low-voltage fault in accelerator pedal / throttle position sensor.

If I stop, put the vehicle in park, shut off the engine, wait about 30-seconds and restart it comes to life with no error lights and drives perfectly like nothing was ever wrong.


I checked all the wires to the throttle body and they look like new (under the dust), no sign of corrosion at all. Does this mean that I need need a new TPS which requires changing the whole throttle body?

On one occasion the check engine (maybe check-tranny?) light also came on and stayed on for about 4 restarts with the car (2 from issue, 2 intentional from just normal driving/parking), but that went off by itself within a day and never came back.

 

There is a known corrosion problem in the electrical connector of the TPS.
That would explain an intermittent failure as you described it.
I would unplug the connector, clean it thoroughly, and see if the problem will occur again...

HTH

David

 

It is my understanding that "low Volts" is often an indication of corrosion when doing diagnostics -- so I would give the contacts another looks. Maybe someone on the forum has an electrical diagram to check to see if other connectors are involved.

It was my understanding that the TB's main problems had been addressed by 2000 so all those discussions would not affect your car. That said The TPS do fail -- and when looking into my one "fail safe" encounter it was noted that the TPS is not available separately -- not good to hear!

Intermittent faults are particularly annoying - good luck

 

Yes, low volts implies that a connection is loose/corroded (or a sensor failure). The throttle position sensor's (TPS) and pedal position sensor's (PPS) connections seem to be especially prone to this. Simply unplugging and re-plugging several times will often scrape the pins clean. For a better, longer solution, spraying with a contact cleaner/lubricant such as from Radio Shack will make the pins stay clean longer.

I suspect as these cars get older, the o-rings in the connectors are beginning to harden up and are allowing moisture in, exascerbating the problem. A year ago, almost every time it rained I was getting an intermittent limp mode (accompanied by many different failure messages) which I finally traced to my TPS connector. Since cleaning, lubing AND adding dielectric grease around the o-ring, it's been fine.

 

Did not know about the PPS -- do tell ......I will check the connection.

 

This is a link that should help but keep in mind that the photos are of an xk8 and the code is different.
http://www.gusglikas.com/AutoRepTB.htm
We have found that this is a reoccurring problem that has developed many different codes. Cleaning the connections has eliminated many of the recent issues. I hope this helps!