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Test Description

WARNING: This page is about a different car, the 2004 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers on the diagnostic table.

  1. 7:  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.
  2. 18:  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 that run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Keep this in mind when reviewing the Capture Info.
DTC P1516

Step Action Yes No
Schematic Reference:  Engine Controls Schematics 
Connector End View References:  Powertrain Control Module (PCM) Connector End Views  or  Engine Controls Connector End Views 
1 Did you perform the Diagnostic System Check-Engine Controls? Go to Step 2  Go to Diagnostic System Check - Engine Controls
2 Are DTCs P1518 and P2135 both set also? Go to DTC P2135 Go to Step 3 
3 Is DTC P2135 set? Go to DTC P2135 Go to Step 4 
4
  1. Turn OFF the ignition for 15 seconds.
  2. Turn ON the ignition, with the engine OFF.
  3. Observe the throttle position (TP) sensor 1 and the TP sensor 2 angle parameters.
  4. Slowly depress the accelerator pedal to wide open throttle (WOT) and slowly return the pedal to the released position.
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
  1. Turn OFF the ignition.
  2. Disconnect the throttle actuator motor harness connector.
  3. Remove the air inlet duct from the throttle body.
  4. Inspect the throttle body and the throttle plate for debris, damage, and tampering that could cause the throttle plate to bind. If debris is found, clean the throttle body and repair the source of contamination. If the throttle body and/or throttle plate is damaged, replace the throttle body. Refer to Throttle Body Assembly Replacement .
Did you find and correct the condition?		 Go to Step 17  Go to Step 6 
6 Manually, slowly open the throttle plate to WOT and return the plate 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 
7 
  1. Turn ON the ignition, with the engine OFF.
  2. Manually, slowly open the throttle blade to WOT and return the plate to the closed throttle position while observing the TP sensor 1 and TP sensor 2 angle parameters on the scan tool.
Does the scan tool indicate both angle parameters increasing as the throttle blade is moved to WOT and decreasing as the throttle blade is moved to the closed position?		 Go to Step 8  Go to Step 15 
8
  1. Turn OFF the ignition.
  2. Disconnect the throttle actuator control (TAC) module harness connector containing the TAC motor circuits.
  3. Turn ON the ignition, with the engine OFF.
  4. Test the TAC motor circuits for a short to voltage, with a DMM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 17  Go to Step 9 
9 Test each TAC motor circuit for an open or for high resistance, with a DMM. 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 Test each TAC motor circuit for a short to ground, with a DMM. 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
  1. Disconnect the other TAC module harness connector.
  2. Test for a short between each TAC motor circuit and all other TAC module circuits, with a DMM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 17  Go to Step 12 
12
  1. Turn OFF the ignition.
  2. Reconnect the TAC module.
  3. Connect a test lamp between the 2 TAC motor circuits at the TAC motor harness connector.
  4. Turn ON the ignition, with the engine OFF and observe the test lamp.
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 17  -
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 Throttle Actuator Control (TAC) Module Replacement .
Did you complete the replacement?		 Go to Step 17  -
17
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze/Frame Failure Records.
Does the DTC run and pass?		 Go to Step 18  Go to Step 2 
18  Observe the Capture Info with a scan tool.
Are there any DTCs that have not been diagnosed?		 Go to Diagnostic Trouble Code (DTC) List System OK
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