FixVault
Home › Chevrolet › 2004 › Epica LS › Repair and Diagnosis › Engine Performance › System › Engine Control System - 2.5L (LBK) - DTC P0404 To DTC P1174 › DTC P0451 › Test Description

Test Description

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

  1. 2:  This step verifies that the condition is present.
  2. 4:  This step tests the 5-volt reference of the FTP sensor.
  3. 5:  This step tests the low reference circuit of the FTP sensor.
Step Action Values Yes No
Schematic Reference:  Engine Controls Schematics 
Connector End View Reference:  Engine Control Module (ECM) 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  Monitor the fuel tank pressure (FTP) sensor voltage with the scan tool.
Is the FTP sensor value within the specified range?		 1.0-2.5 V Go to Step 3  Go to Step 4 
3
  1. Observe the Freeze Frame/Failure Records for this DTC.
  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 4  Go to Intermittent Conditions
4 
  1. Turn ON the ignition, with the engine OFF.
  2. Disconnect the fuel tank harness connector.
  3. Measure the voltage from 5-volt reference circuit of the FTP sensor at the fuel tank harness connector - control module side, to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems.
Is the voltage near the specified value?		 5 V Go to Step 5  Go to Step 6 
5  Measure the voltage from the 5-volt reference circuit to the low reference circuit at the fuel tank harness connector - control module side with a DMM.
Is the voltage near the specified value?		 5 V Go to Step 8  Go to Step 7 
6 Test the 5-volt reference circuit of the FTP sensor for an open or short to ground between the harness connector and the control module. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 5 V Go to Step 13  Go to Step 10 
7 Test the low reference circuit of the FTP sensor for an open, or for high resistance between the harness connector and the control module. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 13  Go to Step 10 
8 Inspect the fuel tank wiring harness for the following conditions:
  • Opens or shorts to ground in the FTP harness connector to the FTP sensor
  • Damaged wiring

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 13  Go to Step 9 
9 Inspect for poor connections at the FTP sensor harness connector, and fuel tank harness connector. 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 13  Go to Step 11 
10 Inspect for poor connections at the harness connector of the control module. 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 13  Go to Step 12 
11 Replace the fuel tank pressure (FTP) sensor.
Did you complete the replacement?		 - Go to Step 13  -
12 Replace the control module. Refer to Engine Control Module (ECM) Replacement .
Did you complete the replacement?		 - Go to Step 13  -
13
  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 14 
14 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
About FixVault