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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1170 (Engine Controls Diagnosis - 6.0L - Alternative Fuels (DTC P0005-DTC P2665)) >> Diagnosis >> DTC P1020: Injector Output Circuit >> Test Description

Test Description

WARNING: This page is about a different car, the 2004 GMC Sierra and 2004 Chevrolet 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. 3:  If DTC P0200 also sets, diagnose P0200 first. A PWM circuit condition between the AF injector relay and the PCM will cause DTCs P0200 and P1020 to set.
  2. 5:  This step determines if the condition is causing an engine misfire. The AF fuel mode relay must be removed in order to prevent a fuel system switch-over.
  3. 6:  This step tests the ignition feed circuit to the AF fuel mode relay. An open ignition feed circuit to the relay will set this DTC.
  4. 7:  This step tests the AF enable circuit to the FICM. An open AF enable circuit between the splice and FICM will set this DTC without an engine misfire.
  5. 9:  This step verifies that the FICM is receiving the PWM input signal from the PCM. The test lamp should blink while the engine is cranking.
DTC P1020

Step Action Yes No
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls Connector End Views or Fuel Injection Control Module Connector End Views
1 Did you perform the Diagnostic System Check Alternative Fuels - Engine Controls? Go to Step 2  Go to Diagnostic System Check - Alternative Fuels (Engine Controls)
2
  1. Turn ON the ignition, with the engine OFF.
  2. Clear the DTC information with a scan tool.
  3. Start and idle the engine.
  4. Observe the DTC information with a scan tool.
Does DTC P1020 set?		 Go to Step 3  Go to Step 4 
3  Is DTC P0200 also set? Go to DTC P0200  Go to Step 5 
4
  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 5  Go to Diagnostic Aids
5 
  1. Turn OFF the ignition.
    2. IMPORTANT: Removal of the AF fuel mode relay may cause other DTCs to set.
  2. Remove the AF fuel mode relay (KL6).
  3. Turn ON the ignition, with the engine OFF.
  4. Clear the DTCs with a scan tool.
  5. Idle the engine at the normal operating temperature.
  6. Monitor the misfire current counters with a scan tool.
Are any of the misfire current counters incrementing?		 Go to Step 9  Go to Step 6 
6  Probe the ignition feed circuit of the AF mode relay coil with a test lamp connected to B+.
Does the test lamp illuminate?		 Go to Step 7  Go to Step 15 
7 
  1. Turn OFF the ignition.
  2. Install the AF fuel mode relay.
  3. Disconnect the fuel injector control module (FICM). Refer to Fuel Injection Control Module Replacement .
  4. Probe the AF enable circuit with a test lamp connected to a good ground.
  5. Turn ON the ignition, with the engine OFF.
Does the test lamp illuminate?		 Go to Step 14  Go to Step 8 
8
  1. Turn OFF the ignition.
  2. Probe the AF enable circuit with a test lamp connected to B+.
Does the test lamp brightly illuminate?		 Go to Step 12  Go to Step 11 
9 
  1. Turn OFF the ignition.
  2. Disconnect the FICM. Refer to Fuel Injection Control Module Replacement .
  3. Probe the pulse width modulated (PWM) input signal circuit which displays the highest number of misfire current counters with a test lamp connected to B+.
  4. Crank the engine.
Does the test lamp blink?		 Go to Step 14  Go to Step 10 
10 Test the PWM input signal circuit for an open or a short to ground between the FICM and the AF injector relay. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual.
Did you find and correct the condition?		 Go to Step 19  Go to Step 13 
11 Test the AF enable circuit for an open between the FICM and the AF fuel mode relay. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual.
Did you find and correct the condition?		 Go to Step 19  Go to Step 13 
12 Test the AF enable circuit for a short to ground between the following:
  • Powertrain control module (PCM) and the splice
  • FICM and the splice
  • AF fuel mode relay and the splice

Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual.
Did you find and correct the condition?		 Go to Step 19  Go to Step 18 
13 Test for an intermittent and for a poor connection at the AF injector relay. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems in the C/K Pickup Service Manual.
Did you find and correct the condition?		 Go to Step 19  Go to Step 16 
14 Test for an intermittent and for a poor connection at the FICM. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems in the C/K Pickup Service Manual.
Did you find and correct the condition?		 Go to Step 19  Go to Step 17 
15 Repair the ignition feed circuit to the AF fuel mode relay coil. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual.
Did you complete the repair?		 Go to Step 19  -
16 Replace the AF injector relay.
Did you complete the replacement?		 Go to Step 19  -
17 Replace the FICM. Refer to Fuel Injection Control Module Replacement .
Did you complete the replacement?		 Go to Step 19  -
18 Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement in Engine Controls in the C/K Pickup Service Manual.
Did you complete the replacement?		 Go to Step 19  -
19
  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 20 
20 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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