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Well ! A tricky one ! I have had constant issues with 'throttle lag' "delayed acceleration' after pressing hard on the accelerator. Just pressing hard once (just BEFORE kickdown switch is reached) even in neutral is
enough to trigger the fault. A key OFF, then ON cycle restores throttle response. No amount of "Throttle or transmission resets" helped (Key on, floor it, key off, wait etc)
I only have 38pin - NO OBD port, so used a generic code scanner with adapter cable (OBD to 38pin with 3 wires connected) The generic code was always P0120 "Throttle/pedal Position Sensor"
Common consensus is to replace the "pedal position sensor" that the throttle cable connects to. Easy enough to change out. The second hand sensor acted the same..... so, I buy a NEW sensor. Same issue. Grrrr I checked all TPS wiring/plugs 5V supply back to ME unit and all seems OK.
So, Much Internet reading and playing with carsoft 7.4 (Carsoft says error 1542 - Pedal value sensor)
Carsoft states to check idle reading 0.2-0.5v and kick down 4.3-4.8v
The live data for "Pedal position signal 1" showed .35v at idle and 4.84v at full throttle. (Key on, engine off) Hmm. Confirmed with voltmeter and backprobing at ME unit. ("Pedal position signal 2" is half of the signal 1 reading)
Check the picture for what i did to get down to 4.55v at full throttle ! I glued (loctite480) in a small (0.8mm) spacer to stop the PPS opening fully !
And it works !! I can now enjoy full throttle ! And kickdown ! Without getting that delayed soggy response afterwards !!
Hope this info helps someone, I now have 2 spare, known good Pedal position sensors that read 'high' at full throttle, although i suspect it may be the ME reading 'high', not the sensors. Regardless, my fix works !
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Slideshow: A one-of-one U.S.-spec Mercedes-Benz SLR McLaren Roadster became even rarer after a factory-backed transformation at McLaren's headquarters.
