P0122

DIAGNOSTIC TROUBLE CODES PO122, PO123
Throttle position sensor, input to control module low/high, no continuity or shorting to ground/batt+.

Fault Symptom.
CHECK ENGINE lamp (MIL) on.

Condition
Voltage from sensor lower than 0.1 V or higher than 4.95 V.

NOTE: If there is no continuity in the circuit, the control module will assume a value corresponding to a throttle opening of 30%.

Diagnostic Procedure.
1. Check the operation of the position sensor by using the ISAT command "THROTT POS SENS0R" in the "READ FUNCTIONS" menu.

With the ignition switch in the Drive position, check that the correct throttle opening is displayed, as follows:
- approx. 12% (0.5 V) when idling, increasing as the accelerator is depressed to approx. 95% (4.5 V) full throttle.

If correct readings are displayed, proceed to step 5.

2. Unplug the connector from the throttle position sensor and, with the ignition switch in the DRIVE position, check that the voltage across pins 1 and 2 of the connector is about 5 V.

If it is not, continue with step 3.
If the voltage is OK, check the resistance of the sensor by taking a reading across pins 1 and 3. The resistance should decrease smoothly and successively, without any jumps or breaks, from about 2.5 kOhms at idling speed to about 0.9 kOhms at full throttle.

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





3. Switch OFF the ignition and connect a BOB between the Motronic control module and it's wiring. Turn the ignition switch to the DRIVE position and check the voltage from the sensor by taking a reading across pins 12 and 30.

The correct voltage is about 5.0 V.

If the voltage is not correct, proceed to step 5.
If the voltage is correct, check the lead between pin 12 (5 V supply) of the control module and pin 1 of the throttle position sensor. Also check the lead between pin 30 (sensor ground) of the control module and pin 2 of the sensor for continuity/shorting.

4. With the throttle position sensor connector plugged in and with the ignition switch in the DRIVE position, check the voltage across pins 30 and 53 of the control module.
The correct voltage is about 0.5 V at idling speed and about 4-5 V at full throttle.

If the voltage is not OK, check the wiring and/or connectors between pin 53 of the control module and pin 3 of the throttle position sensor for continuity/shorting.

5. 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