throttle position sensor issues

2000 xj 4.0l

Over the last 2 months I've gone through 3 of them. Bwd, oem, and cheapie. Each time I replaced it the code went away, this time no such luck. I'm getting codes p0122 and p1694 - low voltage to tps and no engine bus. I checked the wiring harness, couldn't find any rub through. I tested the wires going to the tps, the ground wasn't showing any resistance when checking ohms, (right wire) the middle wire was showing 4.67 volts(pink stripped) and the left wire was showing 5.12 volts (pink wire). When testing I had the tps unplugged. I've heard of issues with clock spring... Not sure where to start from here!

It's and auto transmission too

Your ground should be showing some sort of resistance. If it was 0 ohms then the ground is bad/broken/not hooked up.

Sorry, let me re-word, it was not showing infanite ohms (broken) it was showing low resistance telling me the ground is ok.

Any ideas?

A Clock Spring TPS fault usually sets a P0123 trouble code. Your codes suggest a wiring issue which could be on any one of the 5 volt sensors. You probably need to expand you inspection and testing of the wire harness.


P0122 JEEP - Throttle Position Sensor/Accelerator Position Pedal Circuit Low Input

Possible causes
- Throttle position sensor harness is open or shorted
- Throttle position sensor circuit poor electrical connection
- Faulty throttle position sensor
- Faulty Powertrian Control Module (PCM)

P1694 Fault In Companion Module. No CCD/J1850 bus messages received from the power train control module-Aisin transmission.

Possible Causes:
CCD Bus (-) circuit open between PCM and TCM.
CCD Bus (+) circuit open between PCM and TCM.
Transmission CCD bus wiring damaged.
Faulty TCM.


COMPLAINT: TPS CODE P0123 WILL NOT CLEAR

A late model Jeep with a 2.5 or 4.0 liter engine and the AW4 transmission comes in with the “MIL” Check Engine Light illuminated and a complaint of late shifts. A scan reveals a code P0123, “TPS Voltage High”, is stored. The scan tools data list indicates that the TPS signal wire voltage is at 5.0 volts at closed throttle, and then ranges up to 11.5 volts. A back probe of the TPS signal wire (usually is an Orange/Dk Blue wire), shows 5.7 volts at closed throttle, with a similar rise in voltage as the throttle is opened. A check of the TPS 5 volt supply and ground circuit prove that both of these circuits are good.

A check of the TPS signal wire with the TPS disconnected shows the same 5.7 volts. Inspection of the wiring between the TPS and the PCM and TCM shows no faults. A replacement TPS does not cure the problem, neither does replacement of the PCM or TCM.

CAUSE:
The Switch Sense circuit in the Clock spring in the steering wheel hub has shorted to battery voltage from the horn button circuit. When the Switch Sense Circuit shorts to the 12 volt HORN circuit the TPS signal voltage is driven high and remains there as shown. This is because the 5 volt reference voltage used by the Cruise Control “Switch Sense” circuit and the TPS are shared inside the PCM.

TESTING:
Unplugging a faulty Clock Spring should return TPS voltages to the normal readings.

CORRECTION:
Replace the Clock spring assembly. Once the Clock spring has been replaced be sure to check the sensor 5volt reference voltage at the PCM to insure that circuit has not been damaged by the short to power. Also check the TPS signal range to insure the TPS has not been damaged.

coloradoinsane,

If you don't feel comportable unplugging the clockspring connector, as Tim_MN suggests, you can remove the Horn Relay in your junction block - this will remove the 12 VDC supply to the clockspring.

Here's a partial view of a 2000 XJ Junction Block showing the location of the Horn Relay.



Before removing the Horn Relay, disconnect and stow the battery negative (-) cable.

With the relay removed, check the voltage readings at the TPS again, if they are normal, you have proven what Tim_MN said about a faulty clockspring. You can leave the Horn Relay removed and drive your XJ until you round up a new clockspring. The only component you won't have is your horn(s).

Great info guys! And thanks for the diagram and the idea about the relay, I don't know why I hadn't thought of removing it! I ended up removing the whole harness, cleaning all of the connections, cleaning the sensors, re-wrapping the harness with electric tape, and using plenty of dialectric grease. Drove it a few times and haven't had any problems since. Hopefully its actually fixed and the problem isn't just hiding now.