Audi Q5 2012 – CGLA 2.0L TDI – P0121 Throttle/pedal pos.sensor A circuit Range/performance.
The vehicle was booked in for a service and to check the Engine light on the dashboard. (sounds simple)
The vehicle was scanned with
P0121 Throttle/pedal position sensor A circuit Range/performance.
Fault Code this is a dreaded fault code as it does not pin point to any particular part for further diagnosis other than there is an issue with the throttle system.
Upon test driving the vehicle it was noticed that a very small boost leak noise was heard, this could be the issue of the vehicle not having the right signal from air mass meter and the right amount of air at the manifold.
So steps began to find the boost leak (this was the easy part) but the boost leak was not audible enough to have the common fault code of boost deviation or
Fault code: 16683/P0299/000665 – Boost Pressure Regulation: Control Range Not Reached.
The vehicle had been in an accident a few months ago, to that side of the vehicle, and the boost leak had not been picked up as it was really not noticeable when driven.
The Intercooler was replaced by us and the insurance company paid for the job to be completed.
Following up on the P0121 Throttle/pedal pos.sensor A circuit Range/performance.
After replacement was done, the basic settings had been carried out for boost control etc.
A Test Drive to check the audible noises was done and the engine seamed happy, no fault codes where found after the first test drive, the second test drive showed a pending code for the same, P0121 Throttle/pedal position sensor A circuit Range/performance.
Live Data – at the time not saved
We had looked at the live data stream and found the throttle valve offsets to open and closed to be in the + 13.5% and – 13.2%
We would assume they should be close to 0%
Throttle Valve Adapter offset – Closed – +13.5%
Throttle Valve Adapter offset – Open – -13.2%
No Photo was taken at this point, Sorry
This time we knew it could not be a boost leak so we removed the induction tube to gain access to the throttle motor and we found the images below.
Live Data Fault code detection and Throttle adaption – Basic Settings
After cleaning the intake manifold, EGR, and Throttle body, The Basis setting for throttle body calibration end stops completed and the live data shows the Current Values for a clean throttle body on this CGLA Engine
Test Drive and Hand Over
The Vehicle was then driven a 2 step drive cycle to confirm the fault code is gone and that the vehicle drives correctly and we didn’t have any other fault code pop up as a mystery after the above repair, it is safe to say this one was tried and tested. and Repaired Correctly.
Final Thoughts on The Issue
We had Serviced the vehicle in our workshop for the last 40,000 kms and it was only after the very minor boost leak started that the engine became dirty and blocked the system i wonder how long this engine lasts before having needing an intake manifold clean – like the rest of the late model common rail injection engines seen in todays vehicles ???