Page 1 of 6 <- Back Forward -> Document ID# 317225 1999 Chevrolet/Geo Corvette Print DTC P1515 Control Module Throttle Actuator Position Performance Refer to Cell 20: TP and APP Sensors 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 PCM and the TAC module redundantly monitor the Commanded and Actual throttle position. This DTC sets if the PCM detects the problem. Conditions for Running the DTC DTCs P0601, P0602, P0604, P0606, P1516, P1517, P1518, are not set. DTCs P1120, P1220 and P1221 are not set at the same time or DTCs P1120 and P1220 are not set at the same time. The ignition switch is in the crank or run position. The ignition voltage is greater than 8.5 volts. The TAC system is not in the battery saver mode. Conditions for Setting the DTC The PCM detects that the commanded and actual throttle positions are not within a calibrated range of each other. All above conditions met for less than 1 second. Action Taken When the DTC Sets The PCM will illuminate the Malfunction Indicator Light (MIL) when this diagnostic runs and fails. The Reduced Engine Power message displays on the driver's 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.
Page 2 of 6 A History DTC clears after forty consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures. The PCM battery voltage is interrupted. Clear the MIL/DTC information using a scan tool. Diagnostic Aids Important Remove any debris from the PCM\TAC module connector surfaces before servicing the PCM\TAC module. Inspect the PCM\TAC module connector gaskets when diagnosing/replacing the modules. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion into the PCM\TAC modules. For any test that requires probing the PCM or a component harness connector, use the Connector Test Adapter Kit J 35616-A. Using this kit prevents damage to the harness/component terminals. Refer to Using Connector Test Adapters in Wiring Systems. If you do not find any trouble, inspect for mechanical problems or binding that may be temperature related. Components may not move freely in extreme heat or cold due to the presence of contaminants or ice formation. The following may cause an intermittent: Poor connections; Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems. Corrosion A mis-routed harness A rubbed through wire insulation 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. 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. 5. 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. 20. 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. DTC P1516 - Requested/Actual Throttle Position Performance (TAC) Value
Page 3 of 6 Step Action (s) Yes No 1 2 3 4 Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? Is DTC P1518 and P1221 also set? Is DTC P1221 set? 1. Turn OFF the ignition for 15 seconds. 2. Turn ON the ignition leaving the engine OFF. 3. Monitor the TP sensor 1 and 2 angle in the TAC data list using the scan tool. 4. Slowly depress the accelerator pedal to Wide Open Throttle (WOT) and then slowly return it to closed throttle. Go to Step 2 Go to Powertrain On Board Diagnostic (OBD) System Check Go to DTC P1518 Throttle Actuator Control (TAC) Module Serial Data Circuit Go to Step 3 Go to DTC P1221 Throttle Position (TP) Sensor 1-2 Correlation DTC P1221 Go to Step 4 Does the TP sensor 1 and 2 Angle increase as the pedal is depressed and then decrease as the pedal is released? 1. Turn OFF the ignition. 2. Remove the duct from the Throttle Body Assembly. Go to Diagnostic Aids Go to Step 5 5 Important Disconnecting the Throttle Actuator Control motor connector will cause additional DTCs to set. 3. Disconnect the Throttle Actuator Control motor harness connector. 4. Turn ON the ignition leaving the engine OFF. 5. Open the throttle blade to Wide Open Throttle (WOT) by hand and then close the throttle blade while observing the TP sensor 1 and 2 Angle on the scan tool. Does the TP sensor 1 and 2 Angle increase as the throttle blade is opened and decrease as the
Page 4 of 6 6 throttle is closed? Go to Step 6 Go to Step 17 1. Turn OFF the ignition. 2. Leave the Throttle Actuator Control motor disconnected. 3. Disconnect the TAC module 16-way connector containing the Throttle Actuator control motor circuits. Refer to PCM/TAC Module Replacement. 4. Turn ON the ignition leaving the engine OFF. 5. Measure the voltage from each of the Throttle Actuator Control motor harness connector to the battery ground. Test both Throttle Actuator Control motor circuits using the DMM J 39200. 7 8 9 10 Is any voltage present? 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 J 39200. Does the DMM indicated continuity within the specified range on both circuits? Test the continuity of each Throttle Actuator Control motor circuit to battery ground using the DMM J 39200. Does the DMM indicate continuity? 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 J 39200. Does the DMM indicate continuity? 1. Turn OFF the ignition. 2. Reconnect the TAC Module. 3. Connect the test lamp J 34142-B between the two terminals of the Throttle Actuator Control motor harness connector. 4. Observe the test lamp as the ignition switch is turned ON. Does the test lamp illuminate briefly when the ignition is turned ON? 0-5ohms Go to Step 11 Go to Step 7 Go to Step 8 Go to Step 12 Go to Step 13 Go to Step 9 Go to Step 14 Go to Step 10 Go to Step 15 Go to Step 17
Page 5 of 6 11 Repair the short to voltage on the affected Throttle Actuator Control motor circuit. Refer to Wiring Repairs in Wiring Systems. Go to Step 19 12 Repair the open/high resistance on the affected Throttle Actuator Control motor circuit. Refer to Wiring Repairs in Wiring Systems. Go to Step 19 13 Repair the short to ground on the affected Throttle Actuator Control motor circuit. Refer to Wiring Repairs in Wiring Systems. Go to Step 19 14 Repair the circuits that are shorted together. Refer to Wiring Repairs in Wiring Systems. Go to Step 19 15 1. Inspect for poor connection at the Throttle Actuator Control motor harness connector. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems. 2. If you find a poor connection, repair the condition as necessary. Refer to Repairing Connector Terminals in Wiring Systems. Did you find and correct the condition? Go to Step 19 Go to Step 16 16 Replace the throttle body assembly. Go to Step 19 17 1. Inspect for poor connections at the TAC Module harness connectors. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems. 2. If you find a poor connection, repair the condition as necessary. Refer to Repairing Connector Terminals in Wiring Systems. Did you find and correct the condition? Go to Step 19 Go to Step 18 18 Replace the TAC module. Refer to PCM/TAC Module Replacement. Go to Step 19
Page 6 of 6 19 1. Select the Diagnostic Trouble Code (DTC) option and the Clear DTC Information option using the scan tool. 2. Idle the engine at the normal operating temperature. 3. Select the Diagnostic Trouble Code (DTC) option and the Specific DTC option, then enter the DTC number using the scan tool. 4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text, if applicable. Does the scan tool indicate that this diagnostic ran and passed? Go to Step 20 Go to Step 2 20 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 <- Back Forward -> Document ID# 317225 1999 Chevrolet/Geo Corvette Print