P1221
DTC P1221 Throttle Position (TP) Sensor 1- 2 Correlation
Circuit Description
The throttle position (TP) sensor is mounted on the air control valve assembly (throttle body). The sensor is actually 2 individual TP sensors within 1 housing. Two separate signal, ground and 5 volt reference circuits are used to connect the TP sensor assembly and the throttle actuator control (TAC) module. The 2 sensors have opposite functionality. The TP sensor 1 signal voltage increases as the throttle opens, from below 1.1 volts at 0 percent throttle to above 3.7 volts at 100 percent throttle. The TP sensor 2 signal voltage decreases from above 3.9 volts at 0 percent throttle to below 1.2 volts at 100 percent throttle. Observe also that the signal circuit for TP sensor 1 is pulled up to 5.0 volts and that the signal circuit for TP sensor 2 is pulled to ground within the TAC module. The TAC module converts these different signals to a common scale and continuously compares them to each other to verify proper system operation.
Conditions For Running the DTC
* DTCs P1517, P1518 are not set.
* The ignition is in the crank or run position.
* The ignition voltage is more than 5.23 volts.
Conditions for Setting the DTC
* TP sensor 2 disagrees with TP sensor 1 by more than 7.5 percent.
* All above conditions met for less than 1 second.
Action Taken When the DTC Sets
* The PCM will illuminate the malfunction indicator lamp (MIL) and the Reduced Engine Power light will be on when the diagnostic fails.
* The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records.
* If no other TAC System DTCs are set, the TAC System operates in Reduced Engine Power Mode. If certain TAC System DTCs are set at the same time, the TAC System either defaults to a more tightly restricted mode of operation if the TAC determines that limited safe operation is possible, or the TAC commands the engine to shut down.
Conditions for Clearing the MIL/DTC
* The PCM turns the MIL OFF after 3 consecutive drive trips that the diagnostic runs and does not fail
* A last test failed (current DTC) clears when the diagnostic runs and does not fail
* A History DTC clears after 40 consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures
* The PCM battery voltage is interrupted
Important:: The clear DTC information function may have to be performed twice in order to clear a Throttle Actuator Control System DTC.
* Using a scan tool
Diagnostic Aids
* Inspect for the following conditions that may cause an intermittent:
- Poor connections
- Corrosion
- Misrouted harness
- Rubbed through wire insulation
- Broken wire inside the insulation
- Water intrusion
* Inspect the TAC module connectors for signs of water intrusion. When this occurs, multiple DTCs should be set and no circuit or component problems can be located.
Inspect for adequate terminal tension. Refer to Wiring Repairs Wiring Repairs in Wiring Systems.
* Inspect for further causes of intermittents. Refer to Symptoms Symptoms.
* If a repair is completed and the DTC was cleared using a scan tool on the same ignition cycle, the default action will not clear until an ignition cycle has occurred.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
3. Disconnect the throttle actuator connector before inserting fingers into the throttle bore. Re-install the air inlet duct after repairs are completed.
9. When jumping either of the TP sensor signal circuits to 5 volts should have no effect on any of the other sensor voltages. If the jumpering effects another parameter, there is a problem within the TAC module.
10. When Jumping either TP sensors signal circuit to ground should have no effect on any of the other sensor voltages. If the jumpering effects another parameter, there is a problem within the TAC module.
17. When the TAC module detects a problem within the TAC System, more than one TAC System related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing one individual problem may correct more than one DTC. Keep this in mind when reviewing captured DTC info.
