Circuit Description
Commanded throttle position (based on accelerator pedal position and possibly other limiting factors) is compared to the actual throttle position. The two values should be within a calibrated range of each other. Commanded and Actual throttle position are monitored redundantly within both the PCM and the TAC module. This DTC will set if the problem is detected by the TAC module.
Conditions for Setting the DTC
| • | DTC P1518 not set. |
| • | Ignition switch is in the crank or run position. |
| • | Ignition voltage greater than 5.23 volts. |
| • | Not in battery saver mode. |
| • | The TAC module detects that the commanded and actual throttle positions are not within a calibrated range of each other or the PCM and the TAC cannot determine throttle position or both TP sensors are invalid. |
| • | All above conditions met for less than 1 second. |
Action Taken When the DTC Sets
| • | The PCM will illuminate the MIL and the Reduced Engine Power light will be on when this diagnostic fails. |
| • | The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and/or Failure Records. |
| • | If no other TAC System DTCs are set, the TAC System will operate in Reduced Engine Power mode, and this DTC will be stored. If certain TAC System DTCs are set at the same time, the TAC System will either default to a more tightly restricted mode of operation if it is determined that limited safe operation is possible, or command engine shut down. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn the MIL off after three consecutive drive trips that the diagnostic runs and does not fail. |
| • | A History DTC will clear after forty consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | A last test failed (Current DTC) will clear when the diagnostic runs and does not fail. |
| • | PCM battery voltage is interrupted. |
| Important: The clear DTC info function may have to be performed twice in order to clear a Throttle Actuator Control System DTC. |
| • | Using a scan tool. |
Diagnostic Aids
| • | An intermittent may be caused by the following: |
| • | Poor connections. Check for adequate terminal tension. Refer to Troubleshooting Procedures, Checking Terminal Contact (Body and Accessories/Wiring Systems) for proper procedure. |
| • | Corrosion |
| • | Mis-routed harness. |
| • | Rubbed through wire insulation. |
| • | Broken wire inside the insulation. |
| • | 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. |
| • | Refer to Intermittents under service category 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.
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If the TP Indicated Angle does not follow the movement of the throttle blade, and no TP Sensor DTCs are set, there is a mechanical problem with the throttle shaft or the TP Sensor. Replace the throttle body assembly. Re-install the air inlet duct after you complete the repairs.
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When a problem is detected 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. It is possible that locating and repairing one individual problem may correct more than one DTC. Keep this in mind when reviewing captured DTC info.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
2 |
Important: If DTC P1518 is also set, diagnosis DTC P1518 first.
Does TP sensor 1 and 2 Angle increase as the pedal is depressed and then decrease as the pedal is released? | -- | Go to Diagnostic Aids | |
3 |
Important: Disconnecting the throttle actuator motor connector will cause additional DTCs to set. Does TP sensor 1 and 2 Angle increase as the throttle blade is opened and decrease as the throttle is closed? | -- | ||
4 |
Does the test lamp illuminate briefly when the ignition is turned on? | -- | ||
5 |
Is any voltage present? | -- | ||
6 | Check the harness continuity between the Throttle Actuator and the TAC module for both Throttle Actuator circuits using a DMM J 39200 . Is continuity indicated on both circuits? | -- | ||
7 | Check the harness for continuity between the Throttle Actuator circuits and the battery ground using a DMM J 39200 . Does the DMM indicate continuity? | -- | ||
8 | Check the harness for continuity between the Throttle Actuator circuits and all other circuits in both TAC module connectors using a DMM J 39200 . Does the DMM indicate continuity? | -- | ||
9 | Check for a poor connections/terminal tension at the Throttle Actuator harness connector. Refer to Body and Accessories/Wiring Systems for the proper procedure. Did you find and correct the problem? | -- | ||
10 | Replace the throttle body assembly. Is the action complete? | -- | -- | |
11 | Repair the short to voltage on the affected Throttle Actuator circuit. Refer to Body and Accessories/Wiring Systems. Is the action complete? | -- | -- | |
12 | Repair the open/high resistance on the affected Throttle Actuator circuit. Refer to Body and Accessories/Wiring Systems. Is the action complete? | -- | -- | |
13 | Repair the short to ground on the affected Throttle Actuator circuit. Refer to Body and Accessories/Wiring Systems. Is the action complete? | -- | -- | |
14 | Repair the circuits that are shorted together. Refer to Body and Accessories/Wiring Systems. Is the action complete? | -- | -- | |
15 |
Important:: Program the replacement PCM. Refer to Powertrain Control Module Replacement . Replace the PCM. Is the action complete? | -- | -- | |
16 | Check for poor connections/terminal tension at the TAC Module harness connectors. Refer to Body and Accessories/Wiring Systems for the proper procedure. Did you find and correct the condition? | -- | ||
17 | Replace the TAC Module. Refer to Electronic Throttle Actuator Control Module Replacement . Is the action complete? | -- | -- | |
18 |
Does the scan tool indicate that this diagnostic ran and passed? | -- | ||
19 | Select the Capture Info option and the Review Info option using the scan tool. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to the applicable DTC table | System OK |
