Recently had the typical TPS issues (EML light, occasional limp mode and stalling when coming to a stop) and wanted to get to the bottom of it so I ordered a new one and tested them with a multimeter. I didn't find specific reference values for our car in my searching so figured I'd share to help others troubleshooting the issue, since these sensors are such a common failure item and most people blindly replace them.
There are two failure modes that you are testing for:
The first is a dead spot – if you apply your test leads across pins 1/2 or 2/3 and slowly rotate the inner piece to simulate throttle application, you'll have a dead spot where the multimeter zeroes out.
The second (as was my case), is a drift in the resistance values the sensor puts out as it ages. Based on my understanding the DME is comparing the values from both sensors against each other, along with the readout from the gas pedal which is the third potential failure point in the system. As you can see, not only do the resistance values start drifting up across the board, but the range between the zero and full throttle positions also increases. Once it becomes sufficiently bad, it triggers the EML / limp mode and throws Throttle Position A / B deviation codes.
See below for the readouts – Sensor #1 is a brand new OEM unit made by VNE (BMW logo ground off), sensor #2 was the OE sensor on my throttle actuator, and sensors #3 / #4 were OEM VNE brand replacements that had both failed over time at the top position.
In my case, I had sensors #2 / #3 on the car and was getting EML issues at full throttle where the deviation was becoming too large. I replaced sensor #3 with an old sensor (#4) that I had lying around, and the problem began showing up at even lower throttle as its values had drifted even further. Sensor #2 remains on the car along with the brand new Sensor #1, which seems to be okay so far but it would probably have been wise to replace both at the same time.
There are two failure modes that you are testing for:
The first is a dead spot – if you apply your test leads across pins 1/2 or 2/3 and slowly rotate the inner piece to simulate throttle application, you'll have a dead spot where the multimeter zeroes out.
The second (as was my case), is a drift in the resistance values the sensor puts out as it ages. Based on my understanding the DME is comparing the values from both sensors against each other, along with the readout from the gas pedal which is the third potential failure point in the system. As you can see, not only do the resistance values start drifting up across the board, but the range between the zero and full throttle positions also increases. Once it becomes sufficiently bad, it triggers the EML / limp mode and throws Throttle Position A / B deviation codes.
See below for the readouts – Sensor #1 is a brand new OEM unit made by VNE (BMW logo ground off), sensor #2 was the OE sensor on my throttle actuator, and sensors #3 / #4 were OEM VNE brand replacements that had both failed over time at the top position.
In my case, I had sensors #2 / #3 on the car and was getting EML issues at full throttle where the deviation was becoming too large. I replaced sensor #3 with an old sensor (#4) that I had lying around, and the problem began showing up at even lower throttle as its values had drifted even further. Sensor #2 remains on the car along with the brand new Sensor #1, which seems to be okay so far but it would probably have been wise to replace both at the same time.
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