Got a call from my brother. CEL with P1121 and P1122. I guess I'll start by checking the wiring connections on the throttle body, etc., clear the codes and see if any return...

 

Try disconnecting the plugs- carefully. But first remove neg. battery cable. Never work on modules without doing that. Use contact cleaner on the plugs, dry and reassemble. The engine will rev up a bit initially, then settle down.

 

Hi RSpi,

I don't have the 2003 XJ DTC Summaries manual, but in case it's helpful, here's what the 2001 manual has to say about possible causes of P1121 and P1122:




The schematics show the PPS is grounded through the ECM, so in addition to RJ's recommendation to clean the TB connectors, it might be worth also cleaning the EMS bulkhead ground stud and wire terminals.

Cheers,

Don

 

Those look to be APP (accel. pedal position) not TB/TPS (throttle body/throttle position sensor) codes.

Rather different where to look!!

 

I made the same assumption until I looked at the schematic. On the X308, the PPS is built into the TB assembly (along with the TPS), and it determines pedal position via the accelerator cable.

Cheers,

Don

 

Good grief... how confusing

 

Well, we could still be using carburetors if not for the emission standards, I suppose

http://api.viglink.com/api/click?for...ansmission.pdf
Have a look starting at page 27.

It is important to note that this write up is for the AJ26 engine. The AJ27 is a true drive by wire and does NOT have the mechanical guard. I suppose Jaguar would say they have not made parts available due to the sensitive nature of the throttle control. And... you don't hear claims of "sudden acceleration" for these cars much, so they must have something right.

 

Very nice. Thanks for the info.

Do these cars have throttle body failures often?

 

Yes! There was a recall to change connector pins- opportunity long since passed. So, many time errors are fixed by cleaning and reseating the connectors. Now, apparently some more are failing TPS pots.

 

Thanks again. I cleaned the connectors and all seems well for now... with the throttle. I only drove about 20 miles so far.

Now for the other issue.

 

I could use some pictures and/or video showing how to clean the TPS connector(s). Today on the interstate I got the Failsafe Engine Mode twice, both times occurring when I had to cancel cruise control for traffic. Related to cruise control? Both times I was able to pull over and restart car with no issues. Both times the RPMs seemed to be locked in the 2000 range, uncontrollable with the pedal. The first time no CEL displayed, but after the second time CEL was lit. Once I got home (200 miles later) I was able to pull P1122, and that was the sole code.

When I do get the connectors off, is it safe to use MAF cleaner, or do I need contact cleaner specifically?

 

Use electronic cleaner, it prevents oxidation.

 

This gentleman has quite a few videos detailing his work on an XJ8. Does this look par for the course on cleaning the connectors?

http://youtu.be/1tfj8v6UHRE