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Old 08-19-2014, 02:13 PM   #1
NMBluept's Avatar
Join Date: Jun 2008
Posts: 44
Accelerator Position Sensor

My 2002 Itsaca Horizon, built on a Freightliner XC chassis with a Cummins ISB engine has been getting a Check Engine light and a lack of throttle response. My ScanGauge did not show any stored codes, but I managed to catch it in the act and got a 131, Accelerator Position Sensor Circuit code. This problem seems to be similar to a problem reported last year on this forum titled "Throttle Position Sensor". The OP for that thread had replaced the accelerator position sensor and continued to receive the error so I am hesitant to go down that path. I have removed the pedal position sensor and found it rather uninteresting. It is a sealed unit with a 6 pin connector. It is internally spring loaded to return to the idle position. The Williams Controls documentation shows the sensor to have 2 parts: IVS (Idle Validation Switch) & APS (Accelerator Position Switch). Both parts use a 5 volt source with IVS switching between Idle Active and Throttle Active and the APS picking via what appears to be a potentiometer a portion of the 5 volts to represent the pedal position.
I have begun looking at the Access Freightliner schematics to try and determine where the 5 volts comes from and where the 2 signals go to. So far just burning eyes.

Anyone have any ideas? Does the VDU (or VDC, I have seen it called both) provide the 5 V and signal processing or is there some other module involved, like maybe the ECM? or is the accelerator position sensor a likely cause?

I did find the Accelerator Position Sensor, part # 131856 listed for $106, so might give that a shot.


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Old 08-19-2014, 04:54 PM   #2
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Join Date: Apr 2011
Location: Powell River, B.C.
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On Dodge / Cummins , the 5v was an output from the Cummins ECM. The TPS used there, had a redundant feature, two potentiometers in the one housing, one ramping up from 0>5v the other down 5>0, the ECM monitoring the two for agreement ,any disagreement threw the code.

99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.
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Old 08-19-2014, 04:58 PM   #3
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Maybe you need this info , if you don't already have it .
Attached Files
File Type: pdf Cummins ISB ISC wiring.pdf (404.5 KB, 53 views)
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.
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