Circuit Description
The Throttle Position (TP) sensor circuit provides a voltage signal that changes relative to throttle blade angle. The signal voltage will vary from less than 1 volt at closed throttle to about 4 volts at Wide Open Throttle (WOT). The TP signal is one of the most important inputs used by the PCM for fuel control and most of the PCM-controlled outputs. The PCM monitors throttle position and compares actual throttle position from the TP sensor to a predicted TP value calculated from engine speed. If the PCM detects an excessively low TP sensor signal voltage, DTC P0122 will be set.
Conditions for Setting the DTC
| • | The engine is running. |
| • | TP sensor signal voltage is less than 0.02 volt. |
| • | Above conditions are present for at least 1 second. |
Action Taken When the DTC Sets
| • | The PCM will illuminate the malfunction indicator lamp (MIL) during the first trip in which the diagnostic test has been run and failed. |
| • | The PCM will store conditions which were present when the DTC set as Freeze Frame and Failure Records data. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn OFF the MIL during the third consecutive trip in which the diagnostic has been run and passed. |
| • | The History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC can be cleared by using the scan tool. |
Diagnostic Aids
Check for the following conditions:
| • | Poor connection at PCM. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. |
| • | Damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the throttle position display on the scan tool while moving connectors and wiring harnesses related to the TP sensor. A change in the display will indicate the location of the fault. |
If DTC P0122 cannot be duplicated, the information included in the Fail Records data can be useful in determining vehicle mileage since the DTC was last set. If it is determined that the DTC occurs intermittently, performing DTC P1122 Diagnosis may isolate the cause of the fault.
Test Description
The number(s) below refer to the step number(s) on the Diagnostic Table:
-
This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming .
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Powertrain OBD System Check performed? | -- | ||
2 |
Is TP Sensor display less than the specified value? | 0.16V | ||
3 |
Does the scan tool indicate DTC P0122 failed? | -- | Go to Diagnostic Aids | |
4 |
Is TP Sensor at the specified value? | 5V | ||
5 |
Is the TP Sensor at the specified value? | 5V | ||
6 |
Was a problem found? | -- | ||
7 | Check the 5 Volt Reference A circuit for a poor connection at the PCM and replace terminal if necessary. Refer to Repair Procedures in Electrical Diagnosis. Was a problem found? | -- | ||
8 |
Was a problem found? | -- | ||
9 | Check the TP sensor signal circuit for a poor connection at the PCM and replace terminal if necessary. Refer to Repair Procedures in Electrical Diagnosis. Was a problem found? | -- | ||
10 | Check the TP sensor signal circuit for a poor connection at the TP sensor and replace terminal if necessary. Refer to Repair Procedures in Electrical Diagnosis. Did the terminal require replacement? | -- | ||
11 | Replace the TP sensor. Refer to Throttle Position Sensor Replacement . Is the action complete? | -- | -- | |
Replace the PCM. Important: : The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | ||
13 |
Does the scan tool indicate DTC P0122 failed? | -- | System OK |
