P0123

DTC P0123 Throttle Position (TP) Sensor Diagnostic Chart:

TPS & ECT:

CIRCUIT DESCRIPTION
The Throttle Position (TP) sensor provides a voltage signal that changes relative to throttle blade angle. Signal voltage will vary from 0.2 - 0.74 volts at idle to about 5.0 volts at Wide Open Throttle (WOT).
The sensor signal is one of the most important inputs used by the Powertrain Control Module (PCM) for fuel control and for most of the PCM control outputs.

DIAGNOSTIC TROUBLE CODE (DTC) PO123 WILL SET WHEN
^ TP sensor voltage is greater than 4.8 volts at any time.

Or

^ Engine is running and air flow is less than 15 gm/sec.
^ TP sensor signal voltage is greater than 1.1 volts.
^ DTC P0101 not present.
^ All conditions met for 5 seconds.

ACTION TAKEN (PCM WILL DEFAULT TO)
If a DTC P0123 is set, the PCM will not allow cruise control, 4th gear or Torque Converter Clutch (TCC) operation. The Malfunction Indicator Lamp (MIL) will be illuminated.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. With closed throttle, ignition "ON" or at idle, the Tech 1 scan tool should display under 0.75 volts. A voltage over 1.1 volts is required to set a DTC PO123.
2. With the Throttle Position (TP) sensor disconnected, the TP sensor voltage should go low and a DTC P0122 will set. This test verifies that the PCM and wiring are OK.
3. Checks the sensors 5V reference and ground circuits, if 5 volts is present, the sensor connection or sensor is faulty.
4. If a voltage of greater than 5V is present, the sensor feed circuit may be shorted to voltage. This can be caused by a chafed wire, or a faulty PCM related sensor backfeeding voltage to the PCM.

DIAGNOSTIC AIDS
Refer to Fuel Metering System for TP sensor replacement procedure.

An open in sensor ground CKT 808 may result in DTC P0117 and P0123. Refer to Intermittents in System Diagnosis/Diagnosis by Symptom Intermittents. - Intermittent Malfunctions

By disconnecting PCM sensors while monitoring the sensor feed circuit voltage the fault may be traced to a sensor backfeeding excessive voltage into the PCM.

Check for:
^ Poor connection or damaged harness - Inspect PCM harness connectors for backed out terminal "BF11" or "BE5," improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.
^ Intermittent test - Monitor TP sensor voltage on scan tool while moving related connectors and wiring harness. If the failure is induced, the display will change. This may help to isolate the location of the malfunction.
^ TP sensor scaling - Observe TP sensor voltage display on scan tool while slowly depressing accelerator pedal with engine stopped and ignition "ON." Display should vary from closed throttle TP sensor voltage (0.2 - 0.74 volt) when throttle is closed, to over 4.0 volts (4000 mV) when throttle is held at Wide Open Throttle (WOT) position. Typically, accelerator pedal travel only yields 4.1 or 4.2 volts maximum. If a TP sensor voltage of over 4.8 volts is observed at any point in normal accelerator pedal travel, replace TP sensor.