HELP!! Air suspension on my Navigator

shospeed

Registered
Its a 03 Navigato....

This morning I noticed that the Air compresor didn't turn on when I turned on the car.

I don't get any "check suspention" from the dash, I've also checked the fuses that go under the passenger side door. There is only 2 fuses for the "Air suspention" down there.

Any ideas?

Anything would help.

Thanks
 
I'm not sure on the '03, but it could be a bad compressor or a bad relay (or both).
 
How can I check it?

I've also checked the wires going in to the compressor and it dosent seem to get any power to it.
But the fuses are ok. What I'm I missing?
 
Are you sure it "needs" to go up?

If it's lower than it should be and doesn't go up when the computer tells it to, it should throw a light.
 
Ohh yeah!
That thing is really low to the ground.
So if its not giving me a "check air system" on the dash then the computer "thinks" its ok. So could it be the sensors (both of them at the same time)?
 
Yea a compressor relay won't immediately cause a light. But it should throw the light if it doesn't reach the desired height after a certain period of time.

I think my air ride is getting a bit tired. I wonder if I can convert to a rear-only system with expedition torsion bars and bilstien shocks up front. The OEM damping has sucked since day 1.
 
It should be, the Navi is nothing but a tarted up expedition anyway. But I don't know how the air ride works on this thing. I really don't want to be looking at a light. I wouldn't mind completely manual control (all I'd need to control would be the rear anyway) but I don't want to have to tear the dash out to remove the check suspension bulb.

If I could plug and play a rear-only air ride computer in, i'd be a happy camper.

JP - think you could post a few diagrams of how the air ride on these things work? I know you have that manual - it helped me out big time on the HVAC fix.
 
Dave, is yours rear only or 4 wheel air ride? The rear only setup like on my '99 is stupid simple. I got the kit from American Air Suspension that allows you to manually air up the rear bags in case of a problem. I also installed a new dryer proactively.

Anyways, for the benefit of others as well as you, here is a cut and paste from the manual...

The air suspension system is designed to improve ride, handling and general vehicle performance for static, on-road and off-road driving conditions:

Ride is improved by using an air type spring (the soft ride is inherent).

Handling is improved by maintaining constant vehicle attitude.

The system consists of unique rear air springs, the air compressor, air lines, air spring solenoids, height sensor, air suspension control module, attachments and associated signals derived from both driver and road inputs. With these components and signals, the air suspension control module commands changes in vehicle height that are necessary for the load leveling features.

The load leveling feature rear air suspension (RAS) systems shall automatically make adjustments in vehicle height so that the vehicle is always at trim height and constant front-to-rear vehicle attitudes are maintained over the expected load range of the vehicle. Adjustments in height that are necessary to correct height differences between the vehicle's left and right sides for the RAS system shall be restricted to what can be reliably achieved with one air suspension height sensor.

The system uses one air suspension height sensor, a steering sensor, generic electronic module (GEM) transfer case inputs and other vehicle sensors to measure driver and road inputs. The system changes vehicle height using an air compressor, two air lines and the use of an air spring with an air spring solenoid.

The air suspension system holds vehicle height when the rear hatch or any door is opened. The system stores rear vehicle height the moment any open door is detected. The system then maintains this height regardless of the addition or removal of a load. The system will return to its commanded height when all doors are closed or the vehicle speed exceeds 16 km/h (10 mph).

Air Suspension Switch


The air suspension switch supplies power to the air suspension control module. Without the air suspension control module receiving this power, the load leveling system is inoperative and will not react when the rear of the vehicle is raised or lowered. If the air suspension system is disabled by turning off the air suspension switch, a "CHECK SUSP" will appear in the RH corner of the instrument cluster with the ignition in the run position.

Air Compressor


The RAS air compressor:

  • is not interchangeable with a four-wheel air suspension (4WAS) compressor.
  • consists of the compressor and vent solenoid; neither are replaceable as individual items.
  • is a single cylinder electric motor driven unit that provides pressurized air as required.
  • is powered by a solid state relay which is controlled by the air suspension control module.
  • passes pressurized air through the compressor air drier that contains silica gel (a drying agent). Moisture is then removed from the compressor air drier when vented air passes out of the system during vent operation.
  • air drier has a single port and is not interchangeable with 4WAS compressor air drier.
  • air drier may be replaced separately.
  • incorporates a snorkel that may be replaced separately.

The vent solenoid:

  • allows air to escape from the system during venting actions.
  • is part of the air compressor cylinder head.
  • has a 1,103 kPa (160 psi) internal relief valve.
  • shares a common electrical connector with the air compressor motor.
  • is enclosed in the cylinder head casting, which forms an integral valve housing that allows the valve tip to enter the pressurized side of the system.
  • has an O-ring seal that prevents air leakage past the valve tip.
  • opens when the air suspension control module determines lowering is required.
  • provides an escape route for pressurized air that opens when system pressures exceed safe operating levels.
  • is replaced with the air compressor as a unit.

Air Spring


RAS vehicles use air springs in the rear. The air springs provide a varying spring rate proportional to the systems air pressure and volume. The air suspension system regulates the air pressure in each air spring by compressing and venting the system air. Increasing air pressure (compressing) raises the rear of the vehicle while decreasing air pressure (venting) lowers the rear of the vehicle. Vehicle height is maintained by the addition and removal of air in each air spring through an air spring solenoid installed in the upper spring cap and energized through the air suspension control module.

The two air springs replace the conventional rear coil springs.

Air Suspension Height Sensor


One air suspension height sensor is mounted on the vehicle. The air suspension height sensor sends a voltage signal to the air suspension control module. The output ranges from approximately 4.75 volts at minimum height (when the vehicle is low or in full jounce), to 0.25 volts at maximum height (when the vehicle is high or in full rebound). The air suspension height sensor has a useable range of 80 mm (3.2 in) compared to total suspension travel of 200-250 mm (8 to 10 in) at the wheel. Therefore, the air suspension height sensor is mounted to the suspension at a point where full rear suspension travel at the wheel is relative to 80 mm (3.2 in) of travel at the air suspension height sensor. The air suspension height sensor is attached between the No. 5 frame crossmember (upper socket) and the panhard rod (lower socket). Replace the air suspension height sensor as a unit.

When the air suspension height sensor indicates that the rear of the vehicle is lower than trim under normal driving conditions, the air compressor will turn on and pump compressed air to the air springs. When the sensor indicates that the rear of the vehicle is raised above trim under normal driving conditions, this will cause the air to be vented from the air springs to lower the vehicle back to its trim height level.

Compressor Relay


The compressor relay is energized by the air suspension control module to allow high current to flow from the battery to the compressor motor.

A solid state relay is used in the air suspension system for air compressor control. The relay incorporates a custom power metal oxide semi-conductor field effect transistor (MOSFET) and ceramic hybrid circuitry. The relay switches high current loads in response to low power signals and is controlled by the logic of the air suspension control module.

Air Suspension Control Module

NOTE: The 4WAS air suspension control module is used for the RAS system. The internal processor recognizes external circuitry to determine if it is installed in a 4WAS or a RAS equipped vehicle.

NOTE: The air suspension control module is calibrated with information from the air suspension height sensor. A new or exchanged air suspension control module requires a ride height adjustment calibration process to be performed.

The air suspension control module controls the air compressor motor (through a solid state relay), and the air spring solenoids. The air suspension control module also provides power to the air suspension height sensor. The air suspension control module controls vehicle height adjustments by monitoring the air suspension height sensor, vehicle speed, a steering sensor, acceleration input, the door ajar signal, transfer case signals, and the brake pedal position (BPP) switch. The air suspension control module also conducts all fail-safe and diagnostic strategies and contains self-test and communication software for testing the vehicle and related components.

The air suspension control module monitors and controls the air suspension system through a 32-pin two-way connector. The air suspension control module is keyed so that the air suspension control module cannot be plugged into an incorrect harness. There are two sides of the harness connection to the air suspension control module. Each is uniquely colored and keyed to prevent reversing the connections.

Solenoid Valve, Air Spring


WARNING: Never rotate an air spring solenoid valve to the release slot in the end cap fitting until all pressurized air has escaped from the spring to prevent damage or injury.

The air spring solenoid:

  • allows air to enter and exit the air spring during leveling operations.
  • is electrically operated and controlled by the air suspension control module.
  • is only installed as a unit

Steering Sensor


The steering sensor provides steering rate and position to the air suspension control module through two signals.

Air Lines


The air lines are connected to the air compressor and routed through the chassis of the vehicle to the air springs. There are two air lines on the air load leveling suspension system. The air lines cannot be spliced or repaired if the air lines have been cut or ruptured.
 
More info...

Inspection and Verification


Verify the customer concern.
NOTE: If the door ajar indicator is illuminated when all doors, the liftgate and the liftgate glass are closed, the air suspension will not work correctly. Repair the door ajar indicator; refer to Section 413-09 .

Visually inspect for obvious signs of mechanical and electrical damage.


Visual Inspection Chart Mechanical Electrical
Restricted suspension movement
Excessive vehicle load
Cut, severed or crimped air line(s)
Unmounted height sensor
Damaged air spring(s)
Open fuses:
Central junction box (CJB) Fuse 4 (15A), 6 (5A) and 20 (5A)
Battery junction box (BJB) Fuse 109 (50A)
Loose, corroded or disconnected connectors
Air suspension switch is in the OFF position
Damaged solenoid valve(s)



If the inspection reveals an obvious concern that is readily repaired, correct the concern before continuing with Inspection and Verification.
If the concern remains after the inspection, use NGS Tester connected to the data link connector (DLC) to retrieve continuous diagnostic trouble codes (DTCs) and to execute On-Demand Self-Test diagnostics for the air suspension control module.
If the On-Demand Self-Test is passed and no DTCs are retrieved, go to Symptom Chart to continue diagnostics.
If DTCs are retrieved, go to Air Suspension Control Module Diagnostic Trouble Code (DTC) Index in this section.
If the air suspension control module cannot be accessed by the NGS Tester, go to Pinpoint Test A.

On-Demand Self-Test


Verify that the following conditions are met before performing the On-Demand Self-Test.

All doors, liftgate and liftgate glass must be closed.
The transmission is in PARK.
The brake pedal position (BPP) switch is not pressed during the test and the parking brake is not set.
The accelerator pedal is not pressed during this test.
Fulfill the conditions before starting self-test.
Install a battery charger for the On-Demand Self-Test to prevent battery drain.
Run the air suspension On-Demand Self-Test.
Record all listed DTCs.
Retrieve stored DTCs.
Diagnose any On-Demand Self-Test DTCs first.
Retest and clear DTCs after repair.
Air Suspension Control Module Diagnostic Trouble Code (DTC) Index

Air Suspension Control Module Diagnostic Trouble Code (DTC) Index DTCs Description Source Action
B1318 Battery Voltage Low Air Suspension Control Module GO to Pinpoint Test C .
B1342 Air Suspension Control Module Air Suspension Control Module INSTALL a new air suspension control module; REFER to Module—Air Suspension Control . SET the front ride height; REFER to Air Suspension Initialization (Clear DTC B2140). CLEAR the DTCs. REPEAT the self-test.
B1485 Brake Pedal Input Circuit Battery Short Air Suspension Control Module RERUN On-Demand Self-Test. MAKE SURE that the brake pedal is not pressed. If DTC is returned again, REPAIR brake pedal position (BPP) circuitry.
B1566 Door Ajar Circuit Short to Ground Air Suspension Control Module GO to Pinpoint Test D .
B2140 Initialization Failure (Vehicle Ride Height Not Programmed) Air Suspension Control Module REFER to Air Suspension Initialization (Clear DTC B2140).
C1439 Vehicle Acceleration EEC-V Circuit Failure Air Suspension Control Module GO to Pinpoint Test E .
C1724 Air Suspension Height Sensor Power Circuit Failure Air Suspension Control Module GO to Pinpoint Test F .
C1726 Air Suspension Rear Pneumatic Failure Air Suspension Control Module GO to Pinpoint Test G .
C1760 Air Suspension Rear Height Sensor High Signal Circuit Failure Air Suspension Control Module GO to Pinpoint Test H .
C1770 Air Suspension Vent Solenoid Output Circuit Failure Air Suspension Control Module GO to Pinpoint Test I .
C1790 Air Suspension LR Air Spring Solenoid Output Circuit Failure Air Suspension Control Module GO to Pinpoint Test J .
C1795 Air Suspension RR Air Spring Solenoid Output Circuit Failure Air Suspension Control Module GO to Pinpoint Test K .
C1830 Air Suspension Compressor Relay Circuit Failure Air Suspension Control Module GO to Pinpoint Test L .
C1917 Steering Electronic Variable Orifice (EVO) Out-of-Range Fault Air Suspension Control Module REPAIR EVO steering system. REFER to Section 211-00 .



Air Suspension Control Module Parameter Identification (PID) Index

Air Suspension Control Module Parameter Identification (PID) Index PID Description Expected Values
4WDLOW Generic Electronic Module 4WD Low Signal to Air Suspension Control Module ON, OFF
4WDSYS Signal From Electronic Shift Relay & Diode Module to Air Suspension Control Module YES, NO
ACC_SIG Acceleration Signal to the Air Suspension Control Module notPRE, PRESNT
AS_COMP Air Suspension Compressor Status ON, OFF
AS_GATE Air Suspension Front Solenoid Gate Valve Status (4WAS Only) ON, OFF
AS_VENT Air Suspension Vent Solenoid Valve Status ON, OFF
ASLRSOL or LR_SOL Air Suspension LR Spring Solenoid Valve Status ON, OFF
ASRRSOL or RR_SOL Air Suspension RR Spring Solenoid Valve Status ON, OFF
BOO_AS Brake Pedal Position (BPP) Switch Input to the Air Suspension Control Module ON, OFF
DOOR_AS Door Ajar Input to the Air Suspension Control Module CLOSED, AJAR
F_FILL Air Suspension Front Fill Solenoid Valve Status (4WAS Only) ON, OFF
FHGTSEN Value of Front Air Suspension Height Sensor (4WAS Only) DC voltage value
IGN_AS Ignition RUN/START Input to the Air Suspension Control Module notRUN, RUN
PK/N_SW Park/Neutral Switch Input to the Air Suspension Control Module notP/N, P/N
R_FILL Air Suspension Rear Fill Solenoid Valve Status (4WAS Only) ON, OFF
RHGTSEN Value of Rear Air Suspension Height Sensor DC voltage value
STEER_A Electronic Steering Sensor A Signal to the Air Suspension Control Module HIGH, LOW
STEER_B Electronic Steering Sensor B Signal to the Air Suspension Control Module HIGH, LOW
VBAT_AS Battery Voltage Value to the Air Suspension Control Module DC voltage value
VSS_AS or VSS_ARC Display Vehicle Speed Sensor Input to the Air Suspension Control Module VSS signal in kph or mph
LC_4WDL Latch Seeing 4WD Low Signal to the Air Suspension Control Module CHANGD/NOCHAG
LC_ACC Latch Seeing Acceleration Signal to the Air Suspension Control Module CHANGD/NOCHAG
LC_BOO Latch Seeing Brake Pedal Position (BPP) Switch Signal to the Air Suspension Control Module CHANGD/NOCHAG
LC_DOOR Latch Seeing Door Ajar Signal to the Air Suspension Control Module CHANGD/NOCHAG
LC_IGN Latch Seeing Ignition RUN/START Signal to the Air Suspension Control Module CHANGD/NOCHAG
LC_PK/N Latch Seeing Park/Neutral Switch Input to the Air Suspension Control Module CHANGD/NOCHAG
LC_VSS Latch Seeing Vehicle Speed Sensor (VSS) Signal Input to the Air Suspension Control Module (If Greater Than 56 kph [35 mph]) CHANGD/NOCHAG
LCSTR_A Latch Seeing Electronic Steering Sensor A Signal to the Air Suspension Control Module CHANGD/NOCHAG
LCSTR_B Latch Seeing Electronic Steering Sensor B Signal to the Air Suspension Control Module CHANGD/NOCHAG
OPSTRAT Status of the Air Suspension Operational Strategy (4 Corner or Rear Only System) 4WAS/2WAS


Air Suspension Control Module Active Command Index

Air Suspension Control Module Active Command Index Active Command Display Action
AIR SUSPENSION CONTROL LIFT FRNT ON, OFF (4WAS Only)
VENT FRNT ON, OFF (4WAS Only)
LIFT REAR ON, OFF
VENT REAR ON, OFF (4WAS Only)
COMPRESSR ON, OFF
VENT ON, OFF
FRNT FILL ON, OFF (4WAS Only)
GATEVALVE ON, OFF (4WAS Only)
REAR FILL ON, OFF (4WAS Only)
LR AIRSP ON, OFF
RR AIRSP ON, OFF
LAMP NORM ON, OFF



Symptom Chart

NOTE: Refer to Wiring Diagrams for connector numbers stated in the Pinpoint Tests.

Symptom Chart Condition Possible Sources Action
No communication with the air suspension control module
CJB Fuse 4 (15A), 6 (5A) and 20 (5A).
Circuitry.
Air suspension control module.
Air suspension switch.
GO to Pinpoint Test A .

Unable to enter self-test
Air suspension control module
GO to Pinpoint Test B .

4x2 vehicle returns front air suspension component DTC
Circuitry.
REPAIR Circuit 900 (BK) for possible intermittent short to ground.

Vehicle changes height with the door open
Circuitry.
Air suspension control module.
GO to Pinpoint Test D .

Vehicle raises and/or lowers too slowly
Circuitry.
Rear pneumatic fault.
Air compressor assembly.
Air suspension control module.
GO to Pinpoint Test I .

Uneven vehicle height
Circuitry.
Rear pneumatic fault.
Air compressor assembly.
Air suspension control module.
GO to Pinpoint Test I .

The air compressor continuously cycles with the ignition switch in the Off position and no DTC is set
Circuitry.
Air suspension control module.
Air suspension relay.
GO to Pinpoint Test M .

The air suspension system is inoperative
Circuitry.
GO to Pinpoint Test N .

Excessive air compressor operation
Circuitry.
GO to Pinpoint Test N .

Harsh or bouncy ride
Circuitry.
GO to Pinpoint Test N .

Ride height changes unexpectedly
Circuitry.
GO to Pinpoint Test N .

The air suspension system operates with the air suspension switch in the OFF position
Circuitry.
Switch.
Air suspension control module.
GO to Pinpoint Test O .

Excessive air compressor noise
Silencer.
Wire harness.
Mounting bracket.
GO to Pinpoint Test P .

The compressor is inoperative
BJB Fuse 109 (50A).
Air compressor assembly.
Circuitry.
Air suspension relay.
GO to Pinpoint Test Q .
 
Beautiful info, JP. Mine is the 4WAS - I'd love to convert to rear only, because the front suspension design is hacked together crap - still has torsion bars, just like the RAS models, but it adds an air spring to the crappy OEM underdamped shock. They suck. I think one is leaking, but it's not throwing a light. OEM is the only replacement, and I want bilstiens.

So it sounds like I need to buy bilstiens for a RAS Navi, pick up some torsion bars off of a RAS Navi (should have higher rate than the 4WAS suspension), and figure out which wires to cut.

Soo... I need wiring diagrams. Pinouts of the connectors, at least, just like we have on the site for the "Kale" mod.

"NOTE: The 4WAS air suspension control module is used for the RAS system. The internal processor recognizes external circuitry to determine if it is installed in a 4WAS or a RAS equipped vehicle. " - good stuff! Looks like I can just cut some wires and my computer will still work. I still want to be able to do manual control like I can with my Mark, though. It'll be handy when hooking up my trailer.
 
Back
Top