The predicted throttle position, based on accelerator pedal position (APP) and possibly other limiting factors, is compared to the actual throttle position. The two values should be within a calibrated range of each other. Both the powertrain control module (PCM) and the throttle actuator control (TAC) module redundantly monitor the predicted and actual throttle position. This diagnostic trouble code (DTC) sets if the PCM detects an out of range condition between the predicted and actual throttle position.
• | DTC P1518 is not set. |
• | The ignition is in the crank or run position. |
• | The ignition voltage is greater than 5.23 volts. |
• | The TAC system is not in the battery saver mode. |
• | The TAC module detects that the predicted 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 of the above conditions met for less than 1 second. |
• | The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails. |
• | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records. |
• | The control module commands the TAC system to operate in the Reduced Engine Power mode. |
• | A message center or an indicator displays Reduced Engine Power. |
• | Under certain conditions the control module commands the engine OFF. |
• | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
• | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
• | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
• | Clear the MIL and the DTC with a scan tool. |
• | Inspect the TAC module connectors for signs of water intrusion. If water intrusion occurs, multiple DTCs may set without any circuit or component conditions found during diagnostic testing. |
• | Verify that the starting and charging systems are operating properly. Low system voltage can cause this DTC to set. |
• | When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing an individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Remember this if you review the stored information in Capture Info. |
• | For an intermittent, refer to Intermittent Conditions . |
The numbers below refer to the step numbers on the diagnostic table.
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 condition with the throttle shaft or the TP sensor.
Locating and repairing an individual condition may correct more than 1 DTC.
Step | Action | Yes | No | ||||
---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | |||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | |||||
2 | Are DTCs P1518 and P1221 both set also? | Go to DTC P1518 | Go to Step 3 | ||||
3 | Is DTC P1221 set? | Go to DTC P1221 | Go to Step 4 | ||||
4 |
Does the scan tool indicate both angle parameters increasing as the pedal is depressed to WOT and decreasing as the pedal is released? | Go to Diagnostic Aids | Go to Step 5 | ||||
5 |
Did you find and correct the condition? | Go to Step 17 | Go to Step 6 | ||||
6 | With your hand, slowly open the throttle plate to WOT and back to the closed position several times. Does the throttle plate move smoothly without binding in both directions? | Go to Step 7 | Go to Step 14 | ||||
Does the scan tool indicate both angle parameters increasing as the throttle blade is moved to WOT and decreasing as it is moved to the closed position? | Go to Step 8 | Go to Step 15 | |||||
8 |
Did you find and correct the condition? | Go to Step 17 | Go to Step 9 | ||||
9 | With a DMM, test each TAC motor circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 17 | Go to Step 10 | ||||
10 | With a DMM, test each TAC motor circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 17 | Go to Step 11 | ||||
11 |
Did you find and correct the condition? | Go to Step 17 | Go to Step 12 | ||||
12 |
Did the test lamp illuminate briefly when the ignition was turned ON? | Go to Step 13 | Go to Step 15 | ||||
13 | Inspect for poor connections at the TAC motor harness connector. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems. Did you find and correct the condition? | Go to Step 17 | Go to Step 14 | ||||
14 | Replace the throttle body assembly. Refer to Throttle Body Assembly Replacement . Did you complete the replacement? | Go to Step 15 | -- | ||||
15 | Inspect for poor connections at the TAC module harness connectors. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems. Did you find and correct the condition? | Go to Step 17 | Go to Step 16 | ||||
16 | Replace the TAC module. Refer to Electronic Throttle Actuator Control Module Replacement . Did you complete the replacement? | Go to Step 17 | -- | ||||
17 |
Does the DTC run and pass? | Go to Step 18 | Go to Step 2 | ||||
With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | System OK |