Refer to Engine Controls Schematics for complete circuit details.
Circuit Description
The commanded throttle position, based on accelerator pedal position and possibly other limiting factors, is compared to the actual throttle position. The 2 values should be within a calibrated range of each other. Both the powertrain control module (PCM) and the throttle actuator contorl (TAC) module redundantly monitor the Commanded and Actual throttle position. This diagnostic trouble code (DTC) sets if the TAC module detects the problem.
Conditions for Running the DTC
| • | DTC P1518 is not set. |
| • | The ignition switch is in the crank or run position. |
| • | The ignition voltage is more than 5.23 volts. |
| • | Not in battery saver mode |
Conditions for Setting the DTC
| • | 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 of the above conditions are met for less than 1 second. |
Action Taken When the DTC Sets
| • | The PCM will illuminate the malfunction indicator lamp (MIL) when this diagnostic runs and fails. |
| • | The Reduced Engine Power message displays on the drivers information center. |
| • | The PCM records the operating conditions at the time during which the diagnostic fails. The PCM stores this information 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. 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 OFF the MIL after three consecutive drive trips during which the diagnostic runs and does not fail. |
| • | A last test failed Current DTC will clear when the diagnostic runs and does not fail. |
| • | A History DTC clears after forty consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures. |
| • | Use a scan tool in order to clear the MIL/DTC information. |
Diagnostic Aids
Important:
• Remove any debris from the PCM or TAC module connector surfaces
before servicing the PCM or TAC module. Inspect the PCM or TAC module connector
gaskets when diagnosing or replacing the modules. Ensure that the
gaskets are installed correctly. The gaskets prevent contaminate
intrusion into the PCM or TAC modules. • For any test that requires probing the PCM or a component
harness connector, use the J 35616
connector test adapter kit . Using this kit prevents
damage to the harness/component terminals. Refer to
Using Connector Test Adapters
in Wiring Systems.
| • | The following problems may cause an intermittent: |
| - | Poor connections -- Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
| - | Corrosion |
| - | A mis-routed harness |
| - | A rubbed-through wire insulation |
| - | A broken wire inside of 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. |
| • | Ensure that the starting and charging systems are operating properly. Low system voltage causes this DTC to set. |
| • | 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. |
| • | For an intermittent condition, refer to Symptoms . |
Test Description
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. Re-install the air inlet duct after you complete the repairs.
-
When a condition 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 condition 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 | Is DTC P1518 and P1221 also set? | -- | Go to DTC P1518 Throttle Actuator Control (TAC) Module Serial Data Circuit | |
3 | Is DTC P1221 set? | -- | Go to DTC P1221 Throttle Position (TP) Sensor 1- 2 Correlation DTC P1221 | |
4 |
Does the TP sensor 1 and 2 Angle increase as the pedal is depressed and then decrease as the pedal is released? | -- | Go to Diagnostic Aids | |
Important: Disconnecting the throttle actuator control motor connector will cause additional DTCs to set. Does the TP sensor 1 and 2 Angle increase as the throttle blade is opened and decrease as the throttle is closed? | -- | |||
6 |
Is any voltage present? | -- | ||
7 | Test the continuity of each of the throttle actuator control motor circuit between the throttle actuator control motor and the TAC module 16-way connector using the DMM. Does the DMM indicated continuity within the specified range on both circuits? | 0-5 ohms | ||
8 | Test the continuity of each throttle actuator control motor circuit to battery ground using the DMM. Does the DMM indicate continuity? | -- | ||
9 | Test the continuity of each throttle actuator control motor circuit at the TAC module harness connector and all other circuits in both TAC module connectors using the DMM. Does the DMM indicate continuity? | -- | ||
10 |
Does the test lamp illuminate briefly when the ignition is turned ON? | -- | ||
11 | Repair the short to voltage on the affected throttle actuator control motor circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
12 | Repair the open/high resistance on the affected Throttle Actuator Control motor circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
13 | Repair the short to ground on the affected throttle actuator control motor circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
14 | Repair the circuits that are shorted together. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
15 |
Did you find and correct the condition? | -- | ||
16 | Replace the throttle body assembly. Is the action complete? | -- | -- | |
17 |
Did you find and correct the condition? | -- | ||
18 | Replace the TAC module. Refer to Electronic Throttle Actuator Control Module Replacement . Is the action complete? | -- | -- | |
19 |
Does the scan tool indicate that this diagnostic ran and passed? | -- | ||
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 |
