Diagnostic info below. There's a new compressor module software calibration available. your Cad dealer should be able to complete this. Tell them to punch up c0711 in their service information search window and it's the only bulletin up there. here it is:
#02-03-99-002: Service Air Suspension Message Diagnostic Trouble Code (DTC) C0711 and/or Clicking Noise From Rear of Vehicle with Ignition Off and/or Electronic Controlled Air Suspension (ECAS) Compressor Cycles Too - (Nov 26, 2002)
Models:2003 HUMMER H2with Off Road Suspension Package (RPO ZM6)
Some customers may comment on a Service Air Suspension message and/or a clicking noise from the rear of the vehicle when the vehicle is shut off and the key is removed from the ignition and/or the ECAS compressor cycles too frequently while the vehicle is running.
Cause
ECAS control module calibration issues.
Correction
For diagnosis and repair of the ECAS, follow the service procedure below.
- <LI type=1>For diagnosis of Service Air Suspension DTC C0711, refer to DTC C0711 (SI Document ID #857738).
Important: ? Before reprogramming an Electronic Control Module (ECU), refer to Adm Msg - Important Programming/TIS Information for Technicians (Admin Number 20020120 - 9/10/02) #VSS20020120 (SI Document ID #976439).
? When replacing the ECAS control module, the new module MUST BE reprogrammed.
- Reprogram the ECAS control module with Tech Line Broadcast 11.75 sent to Dealers on 11/16/02 or newer. Refer to the Service Programming System (SPS) Remote Procedure (SI Document ID #820913) or the Service Programming System (SPS) Pass-Thru Procedure (SI Document ID #820915
DTC C0711
Diagnostic Instructions
DTC C0711 00: Level Control Air Pressure Sensor Circuit
Circuit
Short to Ground
Open/High Resistance
Short to Voltage
Signal Performance
Air Suspension Pressure Sensor 5-Volt Voltage Reference
C0711 00
C0711 00
C0711 00
--
Air Suspension Pressure Sensor Signal
C0711 00
C0711 00
C0711 00
C0711 00
Air Suspension Pressure Sensor Low Reference
--
C0711 00
--
--
Circuit Description
The air suspension pressure sensor sends a voltage signal to the air suspension control module that corresponds to a pressure within the range of 30-180 psi. The air suspension control module also uses this signal to verify that the proper amount of pressure is achieved in the air dryer within 23 seconds prior to opening of the inlet valves for inflation of the air springs.
Conditions for Running the DTC
Battery voltage is between 9-16 volts.
Conditions for Setting the DTC
The air suspension module detects that the supplied 5-volt reference voltage circuit for the pressure sensor falls below 4.75 volts or exceeds 5.25 volts.
The air suspension module detects that the signal voltage circuit for the pressure sensor falls below 0.5 volt or exceeds 4.75 volts.
Action Taken When the DTC Sets
? The air suspension system will be inoperative.
? The SERVICE SUSPENSION SYSTEM message will be displayed.
Conditions for Clearing the MIL/DTC
? When the fault is no longer present, DTC C0711 will change from a current DTC to a history DTC on the next ignition cycle.
? DTC C0711 will be cleared from history after 50 ignition cycles.
Diagnostic Aids
Repair all other DTCs before C0711.
This DTC is set when:
? The pneumatic status of the air suspension system is out of limits.
? When excessive amounts of time have elapsed when inflating the air springs.
? When there is a air leak in the system.
? When vehicle speed is greater than 3 km/h (1.8 mph) and rate of height change is out of limits which may be caused by a damaged LR or RR air suspension sensor.
? When the underhood fuse block 60A compressor fuse (ECAS fuse) is open.
? When the compressor relay is defective.
? When there is an intermittent or permanent loss of continuity between the compressor and the compressor supply voltage during an upwards leveling event.
Reference Information
Schematic Reference
Suspension Controls Schematics
Description and Operation
Air Suspension Description and Operation
Electrical Information Reference
Scan Tool Reference
<A href="http://gsi.xw.gm.com/si/showDoc.do?docSyskey=857738&pubCellSyskey=73030&pu bObjSyskey=857738&from=sm&cellId=73030#ss11-857738">
Circuit/System Testing- <LI type=1>Verify that there are no air leaks in the system.
⇒If a leak is found, repair or replace the leaking component as necessary.
<LI type=1>Ignition OFF, remove the ECAS Fuses in the underhood fuse block and disconnect the harness connector at the air pressure sensor. <LI type=1>Test for less than 5.0 ohms between the low reference terminal at the harness connector and ground.
<LI type=1>Ignition ON, verify that 4.8-5.2 volts exists between the 5-volt reference circuit terminal of the harness connector and ground.
<LI type=1>Verify the scan tool Air Pressure Sensor parameter is less than 0.5 volts.
<LI type=1>Install a 3A fused jumper wire between the signal circuit terminal and the 5-volt reference circuit terminal. Verify the scan tool Air Pressure Sensor parameter is greater than 4.8 volts.
<LI type=1>If all circuits test normal, test or replace the valve automatic level control solenoid. Refer to Automatic Level Control Air Compressor Replacement. - Clear the DTCs and verify the system operates normally.
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