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Matt, Mechanical Engineer
Category: Mercedes
Satisfied Customers: 22908
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I have a mercedes 320D CLS. There is a loss of acceleration.

Customer Question

I have a mercedes 320D CLS. There is a loss of acceleration. The diagnostic tester is showing the following fault codes:
PO 243

Any suggestions?
Submitted: 4 years ago.
Category: Mercedes
Expert:  Matt replied 4 years ago.

P0489 =Exhaust Gas Recirculation Throttle Control Circuit 'A' Circuit Low
Possible causes
- Faulty Exhaust Gas Recirculation (EGR) Solenoid
- Exhaust Gas Recirculation (EGR) Solenoid harness is open or shorted
- Exhaust Gas Recirculation (EGR) Solenoid circuit poor electrical connection

P0243 = Mercedes-Benz - Turbo/Super Charger Wastegate Solenoid 'A'

Possible causes
- Faulty wastegate solenoid
- Wastegate solenoid harness is open or shorted
- Wastegate solenoid circuit poor electrical connection

P0638 - Throttle Actuator Control Range/Performance Bank 1

Possible causes
- Drive-by-wire control system malfunction
- Throttle actuator malfunction
- Throttle valve malfunction
- PCM malfunction

to have this many faults I'd suspet that there's a wiring / elcetrical power issue

so I'd 1st check that the main engine earth strap is tight and its connections are clean and if thats OK check that you're getting 13+ v on the battery with the engine running

and if thats OK then check the state of the small earth connections on the engine - the ones from the wiring loom that bolt to the engine with small bolts and ring terminals

and also unplug and inspect the main power relays and fuses for signs of overheating or corroded terminals - so the ones for the ECU and the fuel pump

And also unplug the wiring loom connections in the engine bay one at time and inspect for corroded or recessed pins.

Customer: replied 4 years ago.

Thanks. What about fault PT009. Is that something completely different?

Expert:  Matt replied 4 years ago.
Hello Shirely

that code isn't one that I recognise so I suspect its either not true or a mistranslation by the fault code reader

this can happenwhen a generic code reader is trying to read a body fault or AC fault as the codes for these area aren't well cotrolled like they are for the engines