Service Air Suspension...Again!!! HUMTECH

[jarek m]

Believe it or not I had the same thing happened today:

Symptoms
- service air suspension light
- compressor runs for 20 seconds at start up
- rear end does not come up
- passenger slightly inflated
- driver side empty
- no air coming from driver side line

Already checked
- inflation system goes to well over 100psi
- driver side air bag has no leaks
- both sensors have been recently replaced
- air compressor has been changed year ago
- disconnected the battery for a while with no effect
- raised the body and cycled the compressor without driver inflating or passenger changing air pressure


Mine happened after towing my other SUV for couple hundred miles. Also ever since two years ago I changed one of the air bags then in little while each of the sensors then the compressor I never reset the system, my dealer claims there is no such a procedure!!!(Gold Coast Hummer Dealer)

[HUMTECH]

Well the procedure is lift the rear of the truck, and install the calibration blocks between the bump stop and diff housing (every Hummer dealer should have these as an essential tool) depressurize the air suspension system. With the tech 2 go to chassis, air suspension, special functions and then trim height learn. If everthing is good trim height learned will be displayed. raise the rear off the calibration blocks and remove them. close all doors, run truck and verify system works.

[HUMTECH]

And yes Plano is correct, it should be scanned to be sure prior to forking over a pile of money on parts

[jarek m]

Originally Posted by HUMTECH

And yes Plano is correct, it should be scanned to be sure prior to forking over a pile of money on parts

Thanx HUMTECH!

[14u2nv2]

That's good news Jarek.


Planohummer and Humtech,

I'm having it scanned at the Caddillaic dealer tomorrow.

Is there a list of things(codes/procedures) I should have them check while it's on the Tech 2?

Thanks again,

John

[14u2nv2]

Just got back from the dealer.

It's showing a DTC C0711 --Level Control Air Pressure Sensor Circuit code. Cleared it and got the same code again.

The tech wasn't sure what that code means, and thought it needed a ride height calibration, but they didn't have the calibration blocks. I'm no expert, but I don't think that code sounds like a ride height calibration issue.

I have to admit that I was a little bit concerned when they told me that the air spring was broken because it wasn't connected at the bottom mount when they lifted it on the lift. I had to explain that since there was no air pressure in the air spring, it's not expanded. This dealer was a Hummer dealer until about a year ago and is now Cadillac.

Is the pressure sensor on the compressor assembly, maybe in the photo I posted?

Any tips on deciphering this?


Thanks,

John

[Planohummer]

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 H2

with 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.

1. <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.
2. 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

? Circuit Testing
? Connector Repairs
? Testing for Intermittent Conditions and Poor Connections
? Wiring Repairs

Scan Tool Reference

? Scan Tool Output Controls
? Scan Tool Data List
? Scan Tool Data Definitions

<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

1. <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.
   ⇒If greater than specified, test the low reference circuit for open/high resistance. If the circuit tests normal, replace the air suspension control module. Refer to Automatic Level Control Air Compressor Replacement.
   <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.
   ⇒If less than the specified range, test the 5-volt reference circuit for open/high resistance or a short to ground. If the circuit tests normal, replace the air suspension control module. Refer to Automatic Level Control Air Compressor Replacement.
   ⇒If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the air suspension control module. Refer to Automatic Level Control Air Compressor Replacement.
   <LI type=1>Verify the scan tool Air Pressure Sensor parameter is less than 0.5 volts.
   ⇒If greater than the specified range, test the signal circuit terminal for a short to voltage. If the circuit tests normal, replace the air suspension control module. Refer to Automatic Level Control Air Compressor Replacement.
   <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.
   ⇒If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the air suspension control module. Refer to Automatic Level Control Air Compressor Replacement.
   <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.
2. Clear the DTCs and verify the system operates normally.

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