Diagnostic Trouble Code (DTC) P0123

Throttle Position Sensor High Voltage

 

 

Circuit Know-how

 

  • A 5 volt reference voltage signal and a ground to the Throttle Position (TP) sensor are supplied by the ECM and in return the TP is enabled to send a voltage signal back to the ECM relative to the throttle plate opening.
  • You will find the voltage signal changing from approximately 0.33 volts at closed throttle, to more than 4.3 volts at Wide Open Throttle (WOT).
  • The ECM utilizes the TP signal for controlling the fuel and also for most of the ECM controlled outputs the TP signal is supposed to be one of the most essential inputs used by the ECM for this purpose.

                                                            

When will DTC set?

Task boosted after DTC sets

When will DTC clear?

DTC sets when

1) TP sensor voltage indicates a throttle voltage > 4.9 volts.

1) The Malfunction Indicator Lamp (MIL) will be seen to glow.

1) The MIL will go off after four consecutive ignition cycles where the diagnostic is found running faultlessly.

 

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2) The ECM will begin to record operating conditions when the diagnostic fails.

2) A history DTC will automatically clear after 40 consecutive warm-up cycles faultlessly.

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3) This information will be stored in the Freeze Frame and Failure Records will be boosted.

3) The Scan Tool can be used to unset all DTCs.

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4) A history DTC is stored.

4) If the ECM battery feed is dissociated for more than 10 seconds.

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5) The TP angle will default to 0% when the vehicle speed < 3 km/h (2 mph) and 10% when the vehicle speed >3 km/h (2 mph).

 

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6) You will not see the scan tool showing the default value.

 

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Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

1.The On-Board Diagnostic (EOBD) System Check which is carried out assists the technician to undertake some routine probes and store the freeze frame and failure records data on the scan tool if necessary. This creates an electronic copy of the data taken when as soon the test was done. The information is then stored on the scan tool for future use.

2.When the throttle is closed, the TP sensor voltage reading should be < 0.90 volts. In case there is any discrepancy you need to inspect for a binding or sticking throttle cable.

4.If the TP sensor is de-linked then the TP sensor voltage should read < 0.2 volts when the ECM and wiring are OK.

5.If you inspect the ground circuit with a test light then it will check the circuit and find out if any high resistance causing a DTC P0123 to set is existent.

7.Additional DTCs will be set if there is a shorted 5 volt reference circuit.

11.   The change of the ECM must be reprogrammed. Consult the latest Techline procedure for ECM reprogramming.