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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1070 (Engine Controls Diagnosis - 6.6L (Lb7) (DTCS P0237 To P0611)) >> Diagnosis >> DTC P0540 >> 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 number below refers to the step number on the diagnostic table.

  1. 4:  This step checks for battery voltage output from the IAH relay to the IAH.
DTC P0540

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 Is DTC P0380 also set? - Go to DTC P0380 (Federal RPO FE9, NG1)  or DTC P0380 (California RPO YF5, NE1)  Go to Step 3 
3
  1. Turn OFF the ignition.
  2. Turn ON the ignition, with the engine OFF.
  3. Command the IAH ON and OFF with the scan tool.
  4. Observe the IAH parameter with the scan tool.
Does the scan tool display a voltage near the first specified value with the IAH commanded ON and near the second specified value with the IAH commanded OFF?		 11-13 V, 0.0 V Go to Step 9  Go to Step 4 
4 
  1. Turn ON the ignition, with the engine OFF.
  2. Touch the supply stud of the IAH with a test lamp connected to a good ground. Refer to Troubleshooting with a Test Lamp in Wiring Systems.
  3. Command the IAH ON and OFF with the scan tool.
Does the test lamp illuminate with the IAH commanded ON, and turn OFF with the IAH commanded OFF?		 - Go to Step 9  Go to Step 5 
5
  1. Turn OFF the ignition.
  2. Disconnect the IAH relay connector. Refer to Intake Air Heater (IAH) Relay Replacement (Federal Emissions) or Intake Air Heater (IAH) Relay Replacement (California Emissions) .
  3. Turn ON the ignition, with the engine OFF
  4. Probe the IAH relay harness connector ignition 1 voltage circuit with a test lamp connected to a good ground.
Does the test lamp illuminate?		 - Go to Step 6  Go to Step 10 
6
  1. Verify that the IAH relay harness is disconnected.
  2. Turn ON the ignition, with the engine OFF.
  3. Probe the IAH control circuit of the harness connector with a test lamp connected to battery voltage.
  4. Command the IAH ON and OFF with the scan tool.
Does the test lamp illuminate with the IAH commanded ON, and turn OFF with the IAH commanded OFF?		 - Go to Step 11  Go to Step 7 
7
  1. Verify that the IAH relay harness is disconnected.
  2. Turn ON the ignition, with the engine OFF.
  3. Probe the IAH control circuit with a DMM connected to ground.
Does the voltage measure less than the specified value?		 1 V Go to Step 8  Go to Step 13 
8 Test the IAH control circuit for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 16  Go to Step 14 
9 Test for an open or short to ground on one of IAH supply voltage circuits between the IAH supply stud and the ECM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 16  Go to Step 14 
10 Repair the open or short to ground in the IAH ignition 1 voltage circuit. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 - Go to Step 16  -
11 Test for poor connections at the IAH relay. 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 12 
12 Replace the intake air heater relay. Refer to Intake Air Heater (IAH) Relay Replacement (Federal Emissions) or Intake Air Heater (IAH) Relay Replacement (California Emissions) .
Did you complete the replacement?		 - Go to Step 16  -
13 Repair the short to voltage on the relay control circuit. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 - Go to Step 16  -
14 Test 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 
15 Replace the ECM. Refer to Engine Control Module (ECM) Replacement .
Did you complete the replacement		 - Go to Step 16  -
16
  1. Use a scan tool to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC run and pass?		 - Go to Step 17  Go to Step 2 
17 With a scan tool, observe the stored information, Capture Info.
Does the scan tool display any DTCs that you have not diagnosed?		 - Go to Diagnostic Trouble Code (DTC) List System OK
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