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Test H (Code 54): Unable To Detect Rear Raising

NOTE: For TEST "" pin test connector locations. See Fig 1.
  1. Enter STAR tester Functional Test 31 (compressor relay toggle). See FUNCTIONAL TEST under TESTING & DIAGNOSIS in this article. Compressor should cycle on and off repeatedly during test. If compressor cycles, go to step 9). If compressor does not cycle, DO NOT exit Functional Test 31. Go to next step.
  2. Remove air cleaner assembly and compressor shield. Disconnect compressor electrical connector. Measure voltage between circuits No. 417 (Purple/Orange wire) and circuit No. 57 (Black wire) of compressor harness connector. Meter should pulse between zero volts and battery voltage. See Fig 1. If meter pulses, connect compressor connector. Wait 10 minutes for compressor internal circuit breaker to cool down and close. If compressor does not start to cycle after 10 minutes, replace compressor. Repeat SERVICE BAY DIAGNOSTICS under TESTING & DIAGNOSIS. If meter reads zero volts, DO NOT exit Functional Test 31. Go to next step.
  3. Compressor relay should cycle on and off during this test. If relay cycles, exit Functional Test 31 and go to step 7). If relay does not cycle, exit Functional Test 31 and go to next step.
  4. Remove compressor relay and install horn relay in its place. See TEST "A" COMPRESSOR RELAY CIRCUIT Check. Repeat SERVICE BAY DIAGNOSTICS under TESTING & DIAGNOSIS in this article. If Code 54 is displayed, install relays in original positions and go to next step. If Code 54 is not displayed, install horn relay in original position. Replace compressor relay. Repeat SERVICE BAY DIAGNOSTICS under TESTING & DIAGNOSIS.
  5. Measure voltage between circuit No. 414 (Orange/Red wire) at relay terminal and ground. Meter should indicate battery voltage. If battery voltage is present, go to next step. If zero volts, repair circuit 414 (Orange/Red wire) for open. Repeat SERVICE BAY DIAGNOSTICS under TESTING & DIAGNOSIS.
    Fig 1: Relay Circuit Check
    G90G14312
  6. Turn air suspension switch to OFF position. Disconnect control module connectors. Measure resistance of circuit No. 420 (Dark Blue/Yellow wire) between fuse/relay box and pin No. 23 of control module BLACK connector. Meter should indicate less than 10 ohms. See Figure. If less than 10 ohms, replace control module. Repeat SERVICE BAY DIAGNOSTICS under TESTING & DIAGNOSIS. If 10 ohms or more, repair open in circuit No. 420 (Dark Blue/Yellow wire). Repeat SERVICE BAY DIAGNOSTICS under TESTING & DIAGNOSIS.
  7. Remove air compressor relay from fuse/relay box. Disconnect air compressor connector. Measure resistance of circuit No. 417 (Purple/Orange wire) between fuse/relay box and compressor connector. Resistance should be less than 5 ohms. See Figure. If less than 5 ohms, go to next step. If 5 ohms or more, repair open in circuit No. 417 (Purple/Orange wire). Repeat SERVICE BAY DIAGNOSTICS under TESTING & DIAGNOSIS.
  8. Measure resistance between circuit No. 57 (Black wire) at compressor connector and ground. Resistance should be less than 5 ohms. If resistance is less than 5 ohms, replace compressor assembly. Repeat SERVICE BAY DIAGNOSTICS under TESTING & DIAGNOSIS. If resistance is 5 ohms or more, repair open in circuit No. 57 (Black wire). Repeat SERVICE BAY DIAGNOSTICS under TESTING & DIAGNOSIS.
  9. Enter Functional Test 33. See FUNCTIONAL TEST under TESTING & DIAGNOSIS. Leave air suspension switch ON and raise vehicle on hoist. Feel each spring solenoid valve to see if they are cycling. If valves are cycling, go to test 4). If one or both valves do not cycle, DO NOT exit Functional Test 33. Go to next step.
  10. Disconnect inoperative spring solenoid connector. Measure voltage between both circuits in connector. Meter should pulse between battery voltage and zero volts. If meter pulses, replace inoperative spring solenoid valve. If no voltage pulses, exit Functional Test 33 and go to next step.
  11. Measure voltage between circuit No. 414 (Orange/Red wire) at spring solenoid connector and ground. Meter should indicate battery voltage. If battery voltage is present, go to next step. If zero volts is present, repair open in circuit No. 414 (Orange/Red wire). See Figure.
    NOTE: Repeat SERVICE BAY DIAGNOSTICS under TESTING & DIAGNOSIS to verify repairs.
    Fig 2: Spring Solenoid Control Circuit Check
    G90H14313
  12. Turn air suspension switch to OFF position. Disconnect control module connectors. Measure resistance of spring solenoid control circuit between solenoid connector and control module connector. Meter should indicate less than 10 ohms. If resistance is less than 10 ohms, go to next step. If resistance is 10 ohms or more, repair open in circuit between control module and solenoid valve connector.
    NOTE: Resistance measurements in the following procedure check condition of air spring solenoid valve coil and diode. A digital ohmmeter will not pass enough current through diode to check its condition. Use Rotunda Tester (059-00010) or equivalent analog ohmmeter.
  13. Turn air suspension switch to OFF position. Disconnect control module connectors. Turn air suspension switch to ON position. Measure resistance between pins No. 13 and 1 on control module connectors. Reverse leads and measure resistance again between pins. No. 13 and 1 of control module connectors. Meter should indicate 15-18 ohms one way, and 5-10 ohms less the other way. See Figure. If higher reading is 15-18 ohms and lower reading is 5-10 ohms less than higher reading, replace control module. If both readings are the same or 0-18 ohms, replace defective spring solenoid. Measure resistance between pins No. 25 and 1 on control module connectors. Reverse leads and measure resistance again between pins.No. 25 and 1 on control module connectors. Meter should indicate 15-18 ohms one way, and 5-10 ohms less the other way. See Figure. If higher reading is 15-18 ohms and lower reading is 5-10 ohms less than higher reading, replace control module. If both readings are the same or 0-18 ohms, replace defective spring solenoid.
  14. Leave STAR tester in functional test mode, but do not select test (tester button should be depressed down). Leave air suspension switch in ON position. Making sure STAR tester is within reach, raise vehicle on hoist. Ensure height sensor is attached to both ball studs. Height sensor damage must be repaired before continuing.
  15. Lower vehicle and support on frame. If rear of vehicle is supported by axle, air springs will be damaged during this test. Disconnect air line from air drier. Enter Functional Test 26 (compressor rear). See FUNCTIONAL TEST under TESTING & DIAGNOSIS. Air should flow from air drier while compressor is running. If air flows from air drier, exit Functional Test 26. Connect air line to drier and go to step 17). If little or no air flows from air drier, exit Functional Test 26 and go to next step.
    NOTE: Repeat SERVICE BAY DIAGNOSTICS under TESTING & DIAGNOSIS to verify repairs.
  16. Remove air drier from air compressor. Enter Functional Test 26 (compress rear). See FUNCTIONAL TEST under TESTING & DIAGNOSIS. Air should flow from air drier fitting on compressor while compressor is running. If air flows from compressor, replace air drier. If little or no airflow from compressor, replace compressor assembly.
    CAUTION: Enter Functional Test 26 (compress rear) and fill air springs for about 90 seconds before lowering rear of vehicle.
  17. Raise rear of vehicle. Support rear of vehicle on frame not on axle. Supporting vehicle by frame allows full extension of air springs for leak detection. Enter Functional Test 26 (compress rear). See FUNCTIONAL TEST under TESTING & DIAGNOSIS. Check air lines and air springs for leaks. If leaks are detected, exit Functional Test 26. Repair leaks in air lines and/or replace air spring(s). If no leaks are detected, go to next step.
    NOTE: Air lines are routed along left rocker panel along with fuel and brake lines.
  18. Disconnect air lines at air spring solenoid valves and remove heat shields if equipped. Support rear of vehicle on frame to prevent vehicle from lowering during functional test. Enter Functional Test 26 (compress rear). See FUNCTIONAL TEST under TESTING & DIAGNOSIS. Air should flow from both air lines and from both air spring solenoid valves. If no airflow from air lines, repair blocked air lines. If no airflow from air spring(s), replace air spring (s).
NOTE: Repeat SERVICE BAY DIAGNOSTICS under TESTING & DIAGNOSIS to verify repairs.
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