P0122

DIAGNOSTIC TROUBLE CODES P0122, P0123
Throttle position sensor, input to control module low/high,
No continuity or shorting to ground/batt+.

Fault Symptom.
CHECK ENGINE lamp on, high idling speed.

Condition
Voltage lower than 0.1 V, or
Voltage higher than 4.8 V.

NOTE: Should the throttle position sensor become inoperative, the control module will utilize a signal corresponding to a throttle opening of about 35%.

Diagnostic Procedure.
1. Check the operation of the position sensor by using the ISAT command "THROTTLE POSITION" in the "OBTAIN READOUTS" menu.
With the ignition switch in the DRIVE position, check that the correct throttle opening is displayed, as follows:
- approx. 10% when idling, increasing as the accelerator is depressed to approx. 95% at full throttle.

If correct readings are displayed, proceed to step 6.
If incorrect readings are displayed, continue as described below.

2. Switch OFF the ignition and connect a BOB between the MOTRONIC control module and its wiring.
Turn the ignition switch to the DRIVE position and check the signal voltage from the sensor by taking a reading across pins 53 and 30.
The correct voltage is about 0.6 V in the idling position and about 4.5 V in the full-throttle position.

If the voltage is correct, proceed to step 6.
If the voltage is not correct, continue with step 3.





3. Check the supply voltage to the sensor by taking a reading across pins 12 and 30.
The correct voltage here is 5 V.

If the voltage is incorrect, proceed to step 6.
Otherwise, continue as described below,

4. Switch OFF the ignition and unplug the test cable from the MOTRONIC control module. Also unplug the connector from the position sensor.
Check the cable between the MOTRONIC control module and the position sensor for continuity/shorting.
Rectify any faults in the wiring.

If the wiring is OK, continue as described below.

5. Check the resistance by taking a reading across pins 1 and 3 of the throttle position sensor.
The resistance should decrease smoothly and successively, without any jumps or breaks, from about 2.5 kOhms at idling speed to about 1.3 kOhms at full throttle.

In the event of incorrect resistance, change the position sensor.
If the position sensor is OK, continue with the next step.

6. Clear all trouble codes and drive the car to check whether any trouble codes are generated afresh.

If they are, continue at "Before Control Module Replacement" for further diagnostic instructions. Before Replacing A Control Module