Monaro VXR 6.0 2005 - check engine & safety mode

[X111VXR]

In the past few months my 10,000 mile VXR has been playing me up. Typically either just after starting or when driving and almost always when the throttle peddle is not being pressed the car comes up with check engine and puts itself into safety mode and reduces engine power. Switching car off waiting a minute or so and restarting clears this mode and car will often be fine for the rest of the day!

I have read lots about throttle body cleaning/failures - mine is spotless!

I have an OBD2 reader and there are never any error codes reported or stored in the car! This is also backed up by displaying same codes on dashboard.

I use an Android device and an APP called Torque to read the ECU and running a test mode on the car suggests there maybe an issue with O2 Lambda sensors but I am not totally convinced as it suggests they both fail with exactly the same value !

MID:$01 TID:$05
Rich to Lean sensor switch time(calculated) - O2 Bank 1 Sensor 1
Max: 35,442ms Min: 59,441ms
Test result value: 108ms
FAIL

Any suggestions would be appreciated.

[X111VXR]

Its not the original but it is some years old and if left a couple of weeks without use it does go flat. I will get it checked tomorrow and if necessary replace.

[X111VXR]

I had the battery checked today at Halfords it passed their checks. So for now I will keep the battery in the car and not replace it.

I plan to use the car a lot over the next month or so - so let's see if using it helps!

Thanks for the feedback so far it is really appreciated.

[X111VXR]

FIXED !

I found an entry on this forum which I have copied below which led me to think my car was suffering the same issue so we rewired the throttle body return sense wires to the ECU and hey presto no more limp home mode.

I am delighted to have my car running perfectly again.

Thanks for all your comments/help

============================================================================================================

Thanks to everyone that helped along the way. Monkfish, Blair at dynotorque, Eden Vauxhall and especially Paul at wortec who was eventually the man to fix it. After about a year and a half of problems I finally have a working ute! After Blair and Monkfish ran out of ideas I was a little worried to say the least!

To my limited knowledge I will best describe what the cause was to help others out with similar issues.

Here are the findings paul made:

We have checked the voltage drops across the pedal and throttle body circuits and set up data logging for these circuits, looking at voltage and resistance.

It looks like we have found an event just before the car fails where the voltage on circuit A increases and circuit B does not follow. This error is above the 4% allowed by the PCM so it puts the car in limp home mode.

So it it looks like the problem is from the throttle body to the PCM and not the pedal to PCM.

Paul later on discovered that is was caused by a magnetic field. The cable from the throttle body was being affected by the magnetic field being created by the fan coming on. To fix the problem a section of cable from the throttle body to the pcm was cut out and replaced with new cable which had better resistance better magnetic shielding. The voltage in this cable is now a lot further away from the failure point and the problem has FINALLY been fixed.

Please correct me paul if I have made a mistake.

Thanks again everyone,