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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 991 (Engine Controls Diagnosis - 6.6L (Lb7) (DTCS P0016 To P0236)) >> Diagnosis >> DTC P0168 >> Test Description

Test Description

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. 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. 2:  This step checks for a problem in the fuel cooler that could cause the fuel temperature sensor to increase above the pre-determined specification due to a lack of cooler efficiency.
  2. 5:  This step checks for a voltage above or below the 5 volts supplied by the ECM.
DTC P0168

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 
  1. Inspect the fuel cooler located in front of the fuel tank for debris restricting the airflow or damage to the cooling fins.
  2. Inspect the fuel lines for kinks or damage.
  3. Clean or replace the above listed components as necessary.
Did any of the components require a repair?		 - Go to Step 12  Go to Step 3 
3
  1. Disconnect the air filter outlet duct to access the fuel temperature sensor.
  2. Disconnect the fuel temperature sensor electrical connector.
  3. Turn ON the ignition.
  4. Measure the voltage from the signal circuit of the fuel temperature sensor to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems.
Is the voltage within the specified range?		 4.9-5.1 V Go to Step 4  Go to Step 5 
4
  1. Connect a test lamp to battery voltage.
  2. Probe the low reference circuit of the fuel temperature sensor connector. Refer to Probing Electrical Connectors in Wiring Systems.
Does the test lamp illuminate?		 - Go to Step 7  Go to Step 6 
5 
  1. Turn OFF the ignition.
  2. Disconnect the ECM connector that contains the fuel temperature sensor signal circuit.
  3. Test the signal circuit for the following conditions:
Did you find and correct the condition?		 - Go to Step 12  Go to Step 9 
6
  1. Turn OFF the ignition.
  2. Disconnect the ECM connector that contains the fuel temperature sensor low reference circuit.
  3. Test the fuel temperature sensor low reference circuit for an open or high resistance and repair the circuit as necessary. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 12  Go to Step 9 
7
  1. Disconnect the ECM connector that contains the fuel temperature sensor low reference circuit.
  2. Test the low reference circuit between the fuel temperature sensor and the ECM for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 12  Go to Step 8 
8 Test for an intermittent and for poor connections at the fuel temperature sensor and repair as necessary. 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 12  Go to Step 10 
9 Test for an intermittent and for poor connections at the ECM and repair as necessary. 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 12  Go to Step 11 
10 Replace the fuel temperature sensor. Refer to Fuel Rail Temperature (FRT) Sensor Replacement .
Did you complete the replacement?		 - Go to Step 12  -
11 Replace the ECM. Refer to Engine Control Module (ECM) Replacement .
Did you complete the replacement?		 - Go to Step 12  -
12
  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 13 
13 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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