I have a 1995 SL500. CEL came on - checked codes - MAF out of range. I did the following:
- Checked wiring harness for shorts/opens and intermittants - harness OK
- Cleaned MAF - Reset codes - Ran without CEL for a day - CEL on again
- Checked codes again - MAF out of range
- Ordered Bosch rebuilt AMM
- Car drove ok for a day or two with CEL on then began to stall. Disconnected MAF and the car ran great
- Replaced AMM - CEL went out - car ran great for two days
- After filling up my tank, the car stalled and would not start again
My question is, before I send the AMM back, is there something I sould look at.
I'm driving with the AMM disconnected and the car runs great.
Thanks

Wiring Harness issue; ALL
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But he said he checked the harness and it was OK.

However, I have been fooled more than once by these biodegradable wire harness issues.

Here is how I tested the harness:
- Disconnected the MAF sensor
- Continuity check between each of the five wires and all the others-ok
- Continuity check between each of the wires and chassis - only one grounded as it should be-ok
- Disconnected the large connector next to X11-4
- Checked all five wires for continuity to the large plug -ok
Anything else to check? I don't want to rip the harness up to visually check the wires. Wiring to injectors & cam magnets new and in good shape. No codes for anything but MAF range.
I tried to twist the MAF connector and see if there was an intermittant problem but that is rather difficult to do and see. When the car stalled I also twisted the wire and connector with no results. When I disconnect the MAF sensor, car starts and runs well.
I'm going to re-install everything tonight and see if the problem is still there. Also going to check fuel pressure and get a new gas cap(127000mi). If the problem persists, I will return the AMM for another one. Does anyone know what OBDI code is set by a defective gas cap?
I am trying to find a wiring harness at a resonable price. I rufuse to pay $1600 for a harness when it should of been replaced at MB expense.

Turned out to be the MAF 5 pin connector. The internal O-Ring had deteriorated and kept the connector from seating properly.When I torqued the connector with some force the car would stall. I installed a new O-ring from my junk box - you can now torque the connector all day and it still makes a good connection. It's always the little things - Thanks all.