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Old 06-11-2002, 08:57 PM
TomE500 TomE500 is offline
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Join Date: Aug 2001
Location: Milton MA
Posts: 336
Neil You may wanna read the "Evaluating Electronic Engine Controls" material posted here on the DYI String:

This will give you a general oversight of the codes, how they are stored and how the tech "reads" them.

If you bring your car in now for the tech to read, you will pay $60.00 to see the codes read out for the three items that you posted. It simply means that the on-board computer did not get a definative absolute yet from the sensors throughout the drive train system of the vehicle. In a nutshell: It doesn't know specifically fhat the wuck is wrong yet so it tells the tech to check all three possibilities. The tech will "pull" the harness between the pot and the computer and replace it with one of like kind from a vehicle in the shop similar to yours (91-95 119 engine with ASR) that does not presently show any codes related to the ASR. The tech will take that route first because his training has informed him of the problem with all the harnesses especially that harness because it sits on top of the engine exposed to the most amount of heat and may have deterioated insulation of individual wires hidden by the plastic wrap around the harness. (Note-you said the harness was replaced 10K miles ago-If that harness was also replaced {most likely of all harnesses to fail} I think it would be a safe bet to eliminate that possibility.)

The "Idle control Switch" is also a small pigtail "harness" mounted under the drivers side floor mat. (That is the $41.00 part) My tech replaced that part, cleared the codes, and went about a mile before the "limp mode" re-engaged. Upon returning to the shop, the DTC showed that the brand new one was a possible culprit along with the other two. He was 99% sure at that point that it was the TBA but was reluctant to buy the part only to find out he was 1% wrong and have to eat it. He delivered the vehicle to FMW(authorized MB Dealer) A tech who owns a 500E repeated his initial steps and then replaced the TBA, cleared the codes and the vehicle has operated with no DTCs on ASR related problems since (appx 9 months)

The reason I suggested living with it until it is a full time problem is that it will eventually become just that. If it is the pot, the DTC will point only to that in the code read out. As I said in an earlier post, no one will sell you just the pot and it can not be duplicated to the best of my knowledge. ONLY "authorized" MB rebuilders have access to the components and sub assemblies that make up the "whole" of the TBA. I closely examined the "re-manufactured" TBA that was installed in my vehicle and discerned that the only thing that was replaced was the potentiometer and it's plastic housing. I asked if I could keep the original one and was told I would have to forfeit a $300.00 "core charge" [an eltro-mechanical engineer friend told me that the pot was prolly no more than a $10.00 sub assy]

If you want POM (piece of mind;^), spend the $60.00 bucks. If you are an 8 on the 10 scale of DIY wrenching - DO IT YOURSELF!


Last edited by TomE500; 06-11-2002 at 09:54 PM.
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