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Home >> Chevrolet >> 2004 >> Optra5 LS, Automatic >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Controls - 1.6L (L91) - Symptom Troubleshooting And Diagnosis >> Multiple Engine Control Module Information Sensor DTCs Set >> Test Description
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Test Description

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

  1. 1:  The Diagnostic System Check-Engine Controls prompts the technician to complete some basic checks and store the Freeze Frame and Failure Records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.
  2. 9:  A faulty EGR valve can leak a small amount of current from the ignition feed circuit to the 5-volt reference circuit. If the problem does not exist with the EGR valve disconnected, replace the EGR valve.
  3. 18:  The replacement ECM must be reprogrammed. Refer to the latest Techline procedure for ECM reprogramming.
Step Action Values Yes No
1  Perform the Diagnostic System Check - Engine Controls.
Is the check complete?		 - Go to Step 2  Go to Diagnostic System Check - Engine Controls
2
  1. Turn the ignition switch to LOCK.
  2. Disconnect the engine control module (ECM) connector.
  3. Turn the ignition switch to ON.
  4. Inspect the 5-volt reference circuit for the following conditions:
    • A poor connection at the ECM
    • An open between the ECM connector affected sensor shorted to ground or voltage
  5. If a condition is found, locate and repair the open or short circuit, as needed.
Is a condition found?		 - Go to Step 19  Go to Step 3 
3
  1. Inspect the sensor ground circuit for the following conditions:
    • A poor connection at the ECM or affected sensors
    • An open between the ECM connector and the affected sensors
  2. If a condition is found, repair it as needed.
Is a condition found?		 - Go to Step 19  Go to Step 4 
4 Measure the voltage of the exhaust gas recirculation (EGR) pintle position sensor signal circuit between the ECM harness connector and ground.
Is the voltage near the specified value?		 0 V Go to Step 5  Go to Step 9 
5 Measure the voltage of the manifold absolute pressure (MAP) sensor signal circuit between the ECM harness connector and ground.
Is the voltage near the specified value?		 0 V Go to Step 6  Go to Step 11 
6 Measure the voltage of the throttle position (TP) sensor signal circuit between the ECM harness connector and ground.
Is the voltage near the specified value?		 0 V Go to Step 7  Go to Step 12 
7 Measure the voltage of the intake air temperature (IAT) sensor signal circuit between the ECM harness connector and ground.
Is the voltage near the specified value?		 0 V Go to Step 8  Go to Step 13 
8 Measure the voltage of the engine coolant temperature (ECT) sensor signal circuit between the ECM harness connector and ground.
Is the voltage near the specified value?		 0 V Go to Step 16  Go to Step 14 
9 
  1. Disconnect the EGR valve connector.
  2. Measure the voltage of the EGR pintle position sensor signal circuit between the ECM harness connector and ground.
Is the voltage near the specified value?		 0 V Go to Step 10  Go to Step 15 
10 Replace the EGR valve. Refer to Exhaust Gas Recirculation Valve Replacement (Non European Emissions) or Exhaust Gas Recirculation Valve Replacement (European and North American Emissions) .
Is the replacement complete?		 - Go to Step 19  -
11 Locate and repair the short to voltage in the MAP sensor signal circuit.
Is the repair complete?		 - Go to Step 19  -
12 Locate and repair the short to voltage in the TP sensor signal circuit.
Is the repair complete?		 - Go to Step 19  -
13 Locate and repair the short to voltage in the IAT sensor signal circuit.
Is the repair complete?		 - Go to Step 19  -
14 Locate and repair the short to voltage in the ECT sensor signal circuit.
Is the repair complete?		 - Go to Step 19  -
15 Locate and repair the short to voltage in the EGR pintle position sensor circuit.
Is the repair complete?		 - Go to Step 19  -
16 Measure the voltage of the fuel tank pressure sensor signal circuit between the ECM harness connector and ground.
Is the voltage near the specified value?		 0 V Go to Step 18  Go to Step 17 
17 Locate and repair the short to voltage in the fuel tank pressure sensor signal circuit.
Is the replacement complete?		 - Go to Step 19  -
18  Replace the ECM. Refer to Engine Control Module Replacement .
Is the repair complete?		 - Go to Step 19  -
19
  1. Using the scan tool, clear the DTCs.
  2. Start the engine and idle at normal operating temperature.
  3. Operate the vehicle within the Conditions for Setting the DTCs, as specified in the supporting text.
Does the scan tool indicate that this diagnostic ran and passed?		 - Go to Step 20  Go to Step 2 
20 Check if any additional DTCs are set.
Are any DTCs displayed that have not been diagnosed?		 - Go to Diagnostic Trouble Code (DTC) List System OK
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