W209 CLK270 CDI P0123 error - with car not starting

[Palwan]

Hi, I have a 2005 W209 CLK270 CDI (VIN: WDB2093162F164680)

After a long drive (over 45mins) the car will not start. Then after multiple attempts (between 5 and 20mins) it will finally start with an unstable idle.
This used to happen rarely but now happening very often.
Once i start driving, it is smooth.

The error code I am getting is
P0123 Throttle/Pedal Position Sensor/Switch A circuit High Input

Has anyone had this issue and can you suggest where I start ?
Thanks

 

[mersum1es]

That is unlikely culprit... ECU is not reading pedal signal at start, only after injection is started and certain rpm reached. (Well not 100% of OM647, but I think its same in all OM64X engines).

Two things, cam sensor might be playing up. Usually cam o r crank sensor problems start at hot engine. Now engine is not getting sync it it is not allowed to start,

2nd thing could be that you have fuel leak somewhere, and you fuel pressure is not enough to start, and even after start pressure will not stable for a while. Usually these problems are at cold engine, not hot. Fuel leak culprits are injector (tank) lleaks, quantivy control valve, pressure regulator valve, lift pump or hp pump.

 

[horatio]

Fantastic post above. I will add I replaced the crank sensor on mine when it started intermittently having trouble starting when hot (pig of a job - garage did it). I replaced cam sensor myself at same time because it takes less than a minute. The crank sensor threw an EML & codes.

Replaced fuel pressure regulator because of idle jumping up & down (5 minute job). This left no code.

Replaced clear plastic lines & seals on the HP pump because leaks & general hard starting. No code. Temperature did not affect.

 

[Palwan]

Thanks - my issue seems to happen when the car is hot. As it always starts when not driven after some time.
Are you able to share the actual items ordered and replaced please
Thanks

 

[mersum1es]

If you just want start paying parts darts, first two darts are crank sensor and cam sensor... I would start plugging car on SDS and pull ALL codes, plus see live data hat happens when no-start is present.

 

[Palwan]

thank you