Pinpoint Test H: DTC C1840 - The Scan Tool Indicates Self-Test Failure When Attempting To Carry Out The Self-Test
Vehicle Dynamic Suspension
Pinpoint Tests
Pinpoint Test H: DTC C1840 - The Scan Tool Indicates Self-Test Failure When Attempting to Carry Out the Self-Test
Refer to Wiring Diagram Set 41, Vehicle Dynamic Suspension for schematic and connector information. Diagrams By Number
Normal Operation
In the ON position, a signal is sent from the Vehicle Dynamics Module (VDM) along circuit 417 (VT/OG) to circuit 635 (YE) through the closed air suspension switch. The VDM receives this signal and activates the air suspension system. In the OFF position, this signal is interrupted by the open air suspension switch and the VDM deactivates the air suspension system.
- DTC C1840 (Air Suspension Disable Switch Circuit Failure) - If during the VDM on-demand self test, the air suspension switch is not in the ON position or the VDM detects an open, a short to voltage or a short to ground on the air suspension switch circuit, DTC C1840 will set.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Air suspension switch
- VDM
PINPOINT TEST H: DTC C1840 - THE SCAN TOOL INDICATES SELF-TEST FAILURE WHEN ATTEMPTING TO CARRY OUT THE SELF-TEST
NOTICE: Use the Flex Probe Kit for all test connections to prevent damage to the wiring terminals. Do not use standard multi-meter probes.
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H1 CHECK THE AIR SUSPENSION SWITCH VOLTAGE
- Ignition OFF.
- Disconnect: Air Suspension Switch C4087.
- Ignition ON.
- Measure the voltage between air suspension switch C4087-2, circuit 417 (VT/OG), harness side and ground.
- Is the voltage approximately 5 volts?
Yes
GO to H2.
No
GO to H4.
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H2 CHECK CIRCUIT 635 (YE) FOR AN OPEN
- Disconnect: VDM C2131a.
- Disconnect: VDM C2131b.
- Measure the resistance between air suspension switch C4087-1, circuit 635 (YE), harness side and VDM C2131b-7, circuit 635 (YE), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to H3.
No
REPAIR circuit 635 (YE). CLEAR the DTCs. REPEAT the self-test.
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H3 CHECK CIRCUIT 635 (YE) FOR A SHORT TO GROUND
- Measure the resistance between VDM C2131b-7, circuit 635 (YE), harness side and ground.
- Is the resistance greater than 10,000 ohms?
Yes
GO to H6.
No
REPAIR circuit 635 (YE). CLEAR the DTCs. REPEAT the self-test.
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H4 CHECK CIRCUIT 417 (VT/OG) FOR AN OPEN
- Measure the resistance between air suspension switch C4087-2, circuit 417 (VT/OG), harness side and VDM C2131b-4, circuit 417 (VT/OG).
- Is the resistance less than 5 ohms?
Yes
GO to H5.
No
REPAIR circuit 417 (VT/OG). CLEAR the DTCs. REPEAT the self-test.
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H5 CHECK CIRCUIT 417 (VT/OG) FOR A SHORT TO GROUND
- Measure the resistance between VDM C2131b-4, circuit 417 (VT/OG), harness side and ground.
- Is the resistance greater than 10,000 ohms?
Yes
GO to H6.
No
REPAIR circuit 417 (VT/YE). CLEAR the DTCs. REPEAT the self-test.
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H6 CHECK THE AIR SUSPENSION SWITCH
- Push the air suspension switch to the ON position.
- Measure the resistance between air suspension switch pin 1, component side and pin 2, component side.
- Is the resistance less than 5 ohms?
Yes
GO to H7.
No
INSTALL a new air suspension switch. REFER to Air Suspension Switch Service and Repair. CLEAR the DTCs. REPEAT the self-test.
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H7 VERIFY VDM CONNECTIONS
- Check VDM connectors C2131a and C2131b for damage or loose connections.
- Are the module connections OK?
Yes
INSTALL a new VDM. REFER to Vehicle Dynamics Module (VDM) Service and Repair.
No
REPAIR the VDM connectors. CLEAR the DTCs. REPEAT the self-test.
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