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Home >> Chevrolet >> 2004 >> Optra Base, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - 1.6L (L91) - DTC P0107 To DTC P0335 >> DTC P0123 >> Test Description
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Test Description

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

  1. 2:  This step verifies that a condition exists.
  2. 4:  This step tests for a condition in the signal circuit of the TP sensor. If the TP sensor voltage parameter displays a voltage after the throttle body is disconnected, test for a short to voltage in the signal circuit.
Step Action Values Yes No
Schematic Reference:  Engine Controls Schematics 
Connector End View Reference:  Engine Control Module 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
  1. Turn ON the ignition, with the engine OFF.
  2. Observe the TP sensor voltage parameter with a scan tool.
Is the voltage less than the specified value?
4.9 V Go to Step 3  Go to Step 4 
3
  1. Turn OFF the ignition for 30 seconds.
  2. Start the engine.
  3. Operate the vehicle within the conditions for running the DTC.
Did the DTC fail this ignition?
- Go to Step 4  Go to Intermittent Conditions
  1. Turn OFF the ignition.
  2. Disconnect the throttle body harness connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Observe the TP Sensor voltage parameter with a scan tool.
Is the voltage less than the specified value?
0.1 V Go to Step 5  Go to Step 8 
5 Measure the voltage between the 5-volt reference circuit of the TP sensor and the ECM housing with a DMM.
Is the voltage less than the specified value?
5.2 V Go to Step 6  Go to Step 9 
6 Measure the voltage between low reference circuit of the TP sensor and the ECM housing.
Is the voltage less than the specified value.
1 V Go to Step 7  Go to Step 13 
7
  1. Turn OFF the ignition.
  2. Measure the resistance from the low reference circuit of the TP sensor to the ECM housing, with a DMM.
Is the resistance less than the specified value?
10 Ω Go to Step 11  Go to Step 10 
8 Test the signal circuit of TP sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
- Go to Step 16  Go to Step 12 
9
IMPORTANT: The 5-volt reference circuits are internally and externally connected at the controller. Other sensors that share the 5-volt reference circuit may also have DTCs set. Disconnecting a sensor on the shared 5-volt reference circuit may isolate a shorted sensor. Review the electrical schematic and diagnose the shared circuits and sensors.
Test the 5-volt reference circuit of the TP sensor and all shared 5-volt reference circuits for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.Did you find and correct the condition?
- Go to Step 16  Go to Step 12 
10 Test the low reference circuit of the TP sensor for an open or a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
- Go to Step 16  Go to Step 12 
11 Test for shorted terminals and for poor connections at the throttle body assembly. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
- Go to Step 16  Go to Step 14 
12 Test for shorted terminals and for poor connections at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
- Go to Step 16  Go to Step 15 
13
IMPORTANT: The control module and/or the throttle body assembly may be damaged if the circuit is shorted to battery positive voltage.
Repair the short to voltage in the low reference circuit of the TP sensor. Refer to Wiring Repairs in Wiring Systems.Did you complete the repair?
- Go to Step 16  -
14 Replace the throttle body assembly. Refer to Throttle Body Assembly Replacement .
Did you complete the replacement?
- Go to Step 16  -
15 Replace the ECM. Refer to Engine Control Module Replacement .
Did you complete the replacement?
- Go to Step 16  -
16
  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.
Did the DTC fail this ignition?
- Go to Step 2  Go to Step 17 
17 Are there any DTCs that have not been diagnosed? - Go to Diagnostic Trouble Code (DTC) List System OK