P0123

DIAGNOSTIC TROUBLE CODES P0120, P0121,P0122, P0123 (cars without ETS)
Throttle position sensor, malfunctioning or not working at all

Fault Symptom.
CHECK ENGINE lamp (MIL) on.
Fast idling speed.
A/C compressor not working.


Conditions.
If there is a short circuit/open circuit, a DTC will be generated after 5 seconds.

DIAGNOSTIC PROCEDURE

1. Checking The Operation Of The Throttle Position Sensor
Connect the Scan Tool.
Ignition switch in the ON position.
Select "READ FUNCTIONS"
Select THROTTLE POSITION
The Scan Tool should show a reading of about 10%.

If the reading is OK, continue with point 2.

If the reading is not OK, continue with point 3.

IMPORTANT: The Scan Tool shows the voltage of the throttle position sensor in % of 5 V, not to be confused with PWM.







2. Checking The Linearity Of The Throttle Position Sensor
Depress the accelerator very slowly. Depressing it from the fully released (unactivated) position to the floor (wide open throttle) should take about 20-30 seconds. Observe the Scan Tool display during this process.

The reading should steadily increase from about 10% to about 90%.

IMPORTANT: An internal fault in the throttle position sensor would give a reading of 99% in the event of an open circuit and in the event of shorting to ground a reading of 2% for a brief period.

If the reading is OK, continue with point 5.

If the reading is not OK, change the throttle position sensor.







3. Checking The Electrical Interfaces Of The Throttle Position Sensor
Turn the ignition switch to the ON position and then back to the OFF position.

Unplug the throttle position sensor 3-pin connector.

Take a voltage reading at the connector across
- pin 1 and battery negative about 5 V
- pin-3 and battery negative about 5V
- Battery positive and pin 2 about 12 V.

Check the control module's throttle position input for continuity.
- Select "READ FUNCTIONS".
- Select "THROTTLE POSITION".

The Scan Tool should show a reading of about 99%.

Connect a jumper lead across pins 2 and 3 of the throttle position sensor connector.

The Scan Tool should show a reading of about 0%.

The above tests show whether the control module and wiring as far as the throttle position sensor are in good working order.

If all readings are OK, change the throttle position sensor.

If any reading is not OK, continue with point 4.






4. Checking The Wiring Harness
Check The Wiring harness between the control module and the throttle position sensor's 3-pin connector for continuity.

Check The Wiring for continuity, shorting and stray currents.

If the wiring is OK, continue with point 5.

If the wiring is not OK, rectify the fault.

5. Final Check
Clear the diagnostic trouble code, drive the car on test and check whether the trouble code is generated afresh.

If the DTC is generated again, refer to Before Replacing A Control Module.

If the DTC is not generated again, the action taken to rectify the fault was correct, otherwise the fault is of intermittent nature.