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Pinpoint Test G: The Air Compressor is Inoperative

WARNING: This page is about a different car, the 2009 Mercury Grand Marquis and 2009 Ford Crown Victoria. However, it is still accessible from the selected car via links, so may be relevant.

Refer to appropriate SYSTEM WIRING DIAGRAMS article, Vehicle Dynamic Suspension for schematic and connector information.

Normal Operation 

The vehicle dynamics module (VDM) engages the air compressor relay by providing voltage to the relay along circuit 420 (DB/YE). Ground for the relay is provided along circuit 57 (BK). Fused battery voltage is supplied from battery junction box (BJB) fuse 112 (30A) to the relay along circuit 1053 (LB/PK). When the VDM engages the relay, the fused battery voltage travels through the relay to the air compressor along circuit 538 (GY/RD). The compressor is provided a ground path along circuit 57 (BK).

This pinpoint test is intended to diagnose the following:

PINPOINT TEST G: THE AIR COMPRESSOR IS INOPERATIVE 

NOTE: Use the Flex Probe Kit for all test connections to prevent damage to the wiring terminals. Do not use standard multimeter probes.
  1. G1 CHECK VDM DTCs 
    • Review the VDM DTCs retrieved during Inspection and Verification.
    • Is DTC C1830 present? 
    1. YES  : Go to  G7.
    2. NO  : Go to  G2.
  2. G2 CHECK THE VOLTAGE TO THE AIR COMPRESSOR RELAY 
    • Disconnect: Air Compressor Relay
      • Fig 1: Checking Circuit For Voltage
      GF0013877Courtesy of FORD MOTOR CO.
    • Measure the voltage between air suspension relay cavity 30, circuit 1053 (LB/PK), harness side and ground.
    • Is the voltage greater than 10 volts? 
    1. YES  : Go to  G3.
    2. NO  : VERIFY BJB fuse 112 (30A) is OK. If OK, REPAIR circuit 1053 (LB/PK). CLEAR the DTC. REPEAT the self-test.
  3. G3 CHECK CIRCUIT 538 (GY/RD) FOR AN OPEN 
    • Disconnect: Air Compressor C1179
      • Fig 2: Measuring Resistance
      GF0046743Courtesy of FORD MOTOR CO.
    • Measure the resistance between air compressor relay cavity 87, circuit 538 (GY/RD), harness side and air compressor C1179-2, circuit 538 (GY/RD), harness side.
    • Is the resistance less than 5 ohms? 
    1. YES  : Go to  G4.
    2. NO  : REPAIR circuit 538 (GY/RD). CLEAR the DTC. REPEAT the self-test.
  4. G4 CHECK CIRCUIT 538 (GY/RD) FOR A SHORT TO GROUND 
      Fig 3: Measuring Resistance
      GF0046744Courtesy of FORD MOTOR CO.
    • Measure the resistance between air compressor C1179-2, circuit 538 (GY/RD), harness side and ground.
    • Is the resistance greater than 10,000 ohms? 
    1. YES  : Go to  G5.
    2. NO  : REPAIR circuit 538 (GY/RD). CLEAR the DTC. REPEAT the self-test.
  5. G5 CHECK THE AIR COMPRESSOR GROUND CIRCUIT FOR AN OPEN 
      Fig 4: Checking Circuit For Open
      GF0013887Courtesy of FORD MOTOR CO.
    • Measure the resistance between air compressor C1179-1, circuit 57 (BK), harness side and ground.
    • Is the resistance less than 5 ohms? 
    1. YES  : Go to  G6.
    2. NO  : REPAIR circuit 57 (BK). REPEAT the self-test.
  6. G6 ISOLATE THE AIR COMPRESSOR 
    • Connect: Air Compressor C1179
    • Install a fused jumper wire between air compressor relay cavity 30 and cavity 87.
    • Does the air compressor run? 
    1. YES  : REMOVE the jumper wire. Go to  G7.
    2. NO  : REMOVE the jumper wire. INSTALL a new air compressor. REFER to Air Suspension Compressor . REPEAT the self-test.
  7. G7 CHECK THE AIR COMPRESSOR RELAY GROUND FOR AN OPEN 
    • Disconnect: Air Compressor Relay (if not previously disconnected)
      • Fig 5: Measuring Resistance
      GF0046745Courtesy of FORD MOTOR CO.
    • Measure the resistance between air compressor relay cavity 86, circuit 57 (BK), harness side and ground.
    • Is the resistance less than 5 ohms? 
    1. YES  : Go to  G8.
    2. NO  : REPAIR circuit 57 (BK). CLEAR the DTC. REPEAT the self-test.
  8. G8 CHECK CIRCUIT 420 (DB/YE) FOR AN OPEN 
    • Disconnect: Air Suspension Module C2131a
      • Fig 6: Checking Circuit For Open
      GF0013878Courtesy of FORD MOTOR CO.
    • Measure the resistance between air suspension module C2131a-6, circuit 420 (DB/YE), harness side and air compressor relay cavity 85, circuit 420 (DB/YE), harness side.
    • Is the resistance less than 5 ohms? 
    1. YES  : Go to  G9.
    2. NO  : REPAIR circuit 420 (DB/YE). CLEAR the DTC. REPEAT the self-test.
  9. G9 CHECK CIRCUIT 420 (DB/YE) FOR A SHORT TO GROUND 
      Fig 7: Checking Circuit For Short To Ground
      GF0013879Courtesy of FORD MOTOR CO.
    • Measure the resistance between air suspension module C2131a-6, circuit 420 (DB/YE), harness side and ground.
    • Is the resistance greater than 10,000 ohms? 
    1. YES  : Go to  G10.
    2. NO  : REPAIR circuit 420 (DB/YE). CLEAR the DTC. REPEAT the self-test.
  10. G10 ISOLATE THE AIR COMPRESSOR RELAY 
    • Carry out the mini-ISO relay component test. Refer to COMPONENT TESTING article.
    • Does the air compressor relay pass the test? 
    1. YES  : INSTALL a new air suspension module. REFER to Vehicle Dynamics Module (VDM) . REPEAT the self-test.
    2. NO  : INSTALL a new air compressor relay. CLEAR the DTC. REPEAT the self-test.
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