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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1568 (Engine Controls Diagnostic (DTC P0172 To DTC P0455) -- 5.7L) >> Diagnosis >> DTC P0418 >> Test Description

Test Description

WARNING: This page is about a different car, the 2004 Chevrolet Corvette. 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. 5:  This step tests for voltage at the coil side of the relay.
  2. 6:  This step verifies that the PCM is providing ground to the AIR pump relay.
  3. 8:  This step tests if a ground is constantly being applied to the AIR pump relay.
DTC P0418

Step Action Yes No
Schematic Reference: Engine Controls Schematics
1 Did you perform the Diagnostic System Check-Engine Controls? Go to Step 2  Go to Diagnostic System Check - Engine Controls
2 Inspect the ENG IGN 1 fuse.
Is the ENG IGN 1 fuse open?		 Go to Step 13  Go to Step 3 
3
  1. Turn ON the ignition, with the engine OFF.
  2. Command the secondary air injection (AIR) pump relay ON and OFF with a scan tool.
  3. Listen for a click when the relay operates. Repeat the commands as necessary.
Does the AIR pump relay turn ON and OFF with each command?		 Go to Step 4  Go to Step 5 
4
  1. Observe the Freeze Frame/Failure Records data 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.
Does the DTC fail this ignition?		 Go to Step 5  Go to Intermittent Conditions
5 
  1. Turn OFF the ignition.
  2. Remove the AIR pump relay. Refer to Relay Replacement (Within an Electrical Center) or Relay Replacement (Attached to Wire Harness) in Wiring Systems.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the ignition 1 voltage circuit at the AIR pump relay connector with a test lamp that is connected to a good ground. Refer to Probing Electrical Connectors in Wiring Systems.
Does the test lamp illuminate?		 Go to Step 6  Go to Step 12 
6 
  1. Connect a test lamp between the control circuit of the AIR pump relay and the ignition 1 voltage circuit of the AIR pump relay connector.
  2. Command the AIR pump relay ON and OFF with a scan tool. Refer to Diagnostic Aids for terminal identification.
Does the test lamp turn ON and OFF when commanded with a scan tool?		 Go to Step 10  Go to Step 7 
7 Did the test lamp remain illuminated when the scan tool was commanded ON and OFF? Go to Step 9  Go to Step 8 
8 
IMPORTANT: The AIR pump may be damaged if the control circuit is shorted to voltage.
Test the AIR pump relay control circuit for a short to voltage or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.Did you find and correct the condition?		 Go to Step 14  Go to Step 11 
9
IMPORTANT: The AIR pump may be damage if the control circuit is shorted to ground.
Test the AIR pump relay control circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.Did you find and correct the condition?		 Go to Step 14  Go to Step 17 
10 Test for an intermittent and for a poor connection at the AIR pump 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 18  Go to Step 16 
11 Test for an intermittent and for a poor connection at the powertrain control module (PCM). 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 18  Go to Step 17 
12 Repair the open circuit in the ignition 1 voltage circuit of the AIR pump relay. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 Go to Step 18  -
13
IMPORTANT: The ignition 1 voltage circuit of the AIR pump relay is spiced to other components of the vehicle.
Test all circuits and components that are supplied by the ENG IGN 1 fuse for excessive current draw. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.Did you find and correct the condition?		 Go to Step 18  -
14
  1. Ensure all components are installed and all connections are secured.
  2. Command the AIR pump relay ON and OFF with a scan tool.
Does the AIR pump turn ON and OFF when commanded with a scan tool?		 Go to Step 18  Go to Step 15 
15
  1. Replace the AIR pump. Refer to Secondary Air Injection (AIR) Pump Replacement .
  2. Replace the AIR pump fuse as necessary.
Did you complete the replacement?		 Go to Step 18  -
16 Replace the AIR pump relay.
Did you complete the replacement?		 Go to Step 18  -
17 Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement .
Did you complete the replacement?		 Go to Step 18  -
18
  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.
  5. This DTC will not report a pass. The scan tool status for this DTC will not report a pass. The scan tool will only display if the diagnostic test fails. The repair is not complete if the scan tool indicates that the diagnostic test ran and failed.
Does the DTC fail this ignition?		 Go to Step 2  Go to Step 19 
19 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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