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Home >> Chevrolet >> 2003 >> SSR Base >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Control System - 5.3 (DTC P0068 - P0174) >> Diagnostic Information & Procedures >> DTC P0120: Throttle Position (TP) Sensor 1 Circuit >> Test Description

Test Description

The number below refers to the step number on the diagnostic table.

  1. 33:  When the TAC module detects a condition 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 condition may correct more than one DTC. Disconnecting components during testing may set additional DTCs. Keep this in mind when reviewing the stored information, Capture Info.
DTC P0120

Step Action Values Yes No
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls Component Views or Powertrain Control Module (PCM) 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
  1. Turn OFF the ignition.
  2. Remove the air inlet duct from the throttle body.
  3. Disconnect the throttle body harness connector.
  4. Connect the jumper wires between the throttle position (TP) sensor 1 terminals of the throttle body harness connector and the corresponding TP sensor 1 terminals of the throttle body.
  5. Turn ON the ignition, with the engine OFF.
  6. Close the throttle blade by hand.
  7. Observe the TP sensor 1 voltage with a scan tool.
Is the TP sensor 1 voltage within the specified range?		 0.37-0.71 V Go to Step 5  Go to Step 3 
3
  1. Turn OFF the ignition.
  2. Connect jumper wires between the TP sensor 2 terminals of the throttle body harness connector and the corresponding TP sensor 2 terminals of the throttle body.
  3. Turn ON the ignition, with the engine OFF.
  4. Close the throttle blade by hand.
  5. Observe the TP sensor 2 voltage with a scan tool.
Is the TP sensor 2 voltage within the specified range?		 0.28-0.81 V Go to Step 9  Go to Step 4 
4 Is DTC U0107 also set? - Go to Diagnostic Trouble Code (DTC) List Go to Step 9 
5
  1. Open the throttle blade to wide open throttle (WOT) by hand.
  2. Observe the TP sensor 1 voltage parameter on the scan tool.
Is the TP sensor 1 voltage parameter more than the specified value?		 4.51 V Go to Step 9  Go to Step 6 
6
  1. Disconnect the TP sensor harness connector.
  2. Disconnect the throttle actuator control (TAC) module harness connector containing the TP sensor circuits.
  3. Test the TP sensor low-reference 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 32  Go to Step 7 
7
  1. Turn OFF the ignition for 15 seconds.
  2. Connect the TAC module harness connector.
  3. Connect the throttle body harness connector.
  4. Install the air inlet duct.
  5. Turn ON the ignition, with the engine OFF.
  6. Select the DTC Info option on the scan tool.
  7. Lightly touch and move the related engine wiring harnesses and connectors for the TP sensor while observing the DTC Info. The DTC will set if an intermittent condition is present. Refer to Connector Repairs and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 32  Go to Step 8 
8
  1. Continue to observe the DTC Info.
  2. Slowly depress the accelerator pedal to WOT, then slowly return the pedal to the released position 3 times.
Does the scan tool indicate this DTC failed this ignition?		 - Go to Step 27  Go to Diagnostic Aids
9
  1. Disconnect the TP sensor harness connector.
  2. Measure the voltage at the TP sensor 1 signal circuit with a DMM connected to ground.
Is the voltage within the specified range?		 3.94-6.06 V Go to Step 14  Go to Step 10 
10
  1. Turn OFF the ignition.
  2. Disconnect the TAC module harness connector containing the TP sensor circuits.
  3. Turn ON the ignition, with the engine OFF.
  4. Test the TP sensor 1 signal circuit 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 32  Go to Step 11 
11 Test the TP sensor 1 signal circuit for an open or 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 32  Go to Step 12 
12 Test the TP sensor 1 signal 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 32  Go to Step 13 
13
  1. Disconnect the other TAC module harness connector.
  2. Test for a short between the TP sensor 1 signal 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 32  Go to Step 28 
14 Measure the voltage from the TP sensor 1 5-volt reference circuit to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems.
Is the voltage within the specified range?		 4.54-5.21 V Go to Step 24  Go to Step 15 
15 Is the voltage more than the specified value? 5.21 V Go to Step 16  Go to Step 18 
16
  1. Turn OFF the ignition.
  2. Disconnect the TAC module harness connector containing the TP sensor circuits.
  3. Turn ON the ignition, with the engine OFF.
  4. Test the TP sensor 1 5-volt reference circuit 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 32  Go to Step 17 
17
  1. Turn OFF the ignition.
  2. Disconnect the accelerator pedal position (APP) sensor harness connector.
  3. Disconnect the other TAC module harness connector.
  4. Turn ON the ignition, with the engine OFF.
  5. Test the APP sensor 1 5-volt reference circuit 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 32  Go to Step 22 
18 Disconnect the APP sensor.
Is the voltage less than the specified value?		 4.54 V Go to Step 19  Go to Step 30 
19
  1. Disconnect the TAC module harness connector containing the TP sensor circuits.
  2. Test the TP sensor 1 5-volt reference circuit for an open or 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 32  Go to Step 20 
20 Test the TP sensor 1 5-volt reference circuit for a short to ground with a DMM.
Did you find and correct the condition?		 - Go to Step 32  Go to Step 21 
21 Test the APP sensor 1 5-volt reference 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 32  Go to Step 22 
22 Test for a short between the TP sensor 1 5-volt reference 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 32  Go to Step 23 
23 Test for a short between the APP sensor 1 5-volt reference 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 32  Go to Step 28 
24
  1. Connect a fused jumper between the TP sensor 1 low reference circuit and the TP sensor 1 signal circuit.
  2. Observe the TP sensor 1 voltage parameter with a scan tool.
Is the TP sensor 1 parameter near the specified value?		 0 V Go to Step 26  Go to Step 25 
25
  1. Turn OFF the ignition.
  2. Disconnect the TAC module harness connector containing the TP sensor circuits.
  3. Test the TP sensor 1 low-reference circuit for an open or 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 32  Go to Step 28 
26 Inspect for an intermittent and for a poor connection at the throttle body 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 32  Go to Step 29 
27 Inspect for an intermittent and for a poor connection at the APP sensor 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 32  Go to Step 30 
28 Inspect for an intermittent and for a poor connection at the TAC module 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 32  Go to Step 31 
29 Replace the throttle body assembly. Refer to Throttle Body Assembly Replacement .
Did you complete the replacement?		 - Go to Step 32  -
30 Replace the APP sensor. Refer to Accelerator Pedal with Position Sensor Replacement .
Did you complete the replacement?		 - Go to Step 32  -
31 Replace the TAC module. Refer to Throttle Actuator Control (TAC) Module Replacement .
Did you complete the replacement?		 - Go to Step 32  -
32
  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.
Did the DTC fail this ignition?		 - Go to Step 2  Go to Step 33 
33  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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