Transfer Case
Four Wheel Drive (4WD) Systems
Pinpoint Test F: DTC P1635
Normal Operation
The All-Wheel Drive (AWD) system continuously monitors vehicle conditions and automatically adjusts the torque distribution between the front and rear wheels. During normal operation, most of the torque is delivered to the front wheels. If wheel slip between the front and rear wheels is detected, or if the vehicle is under heavy acceleration, the AWD (All-Wheel Drive) system increases torque to the rear wheels to prevent or control wheel slip. When the AWD (All-Wheel Drive) system is functioning properly, there should be no perceived speed difference between the front and rear axles when launching or driving the vehicle on any uniform surface. Traction should be similar to a part time Four-Wheel Drive (4WD) system in 4H (4X4 HIGH), but have no binding in turns.
If the spare tire is installed, the AWD (All-Wheel Drive) system may disable automatically and enter front wheel drive only mode to protect driveline components. This condition may be indicated by an AWD (All-Wheel Drive) OFF message in the message center.
If there is an AWD (All-Wheel Drive) OFF message in the message center from using the spare tire, this indicator should turn off after reinstalling the repaired or replaced normal road tire and driving a short distance. It is recommended to reinstall the repaired or replaced road tire as soon as possible. If the sizes of the tires used on the front or rear axles differ greatly enough, the AWD (All-Wheel Drive) system could stop functioning and default to Front Wheel Drive (FWD) or damage to AWD (All-Wheel Drive) system could occur.
If road tires are installed that are larger than the tires originally available with the vehicle (upsized), the AWD (All-Wheel Drive) system may be damaged when the mini spare is installed. Therefore, to prevent damage to the AWD (All-Wheel Drive) system, larger tires than were originally available with the vehicle should not be used. In addition, a spare tire smaller than the originally supplied spare tire should not be used.
- DTC P1635 (Tire/Axle Out of Acceptable Range)- When the 4X4 control module detects an inappropriate size mini spare or road wheels/tires (greater than 7% difference in size across the front and rear axle or greater than 14% difference in size at one wheel on either the front or rear axle) installed, this DTC will be set.
This pinpoint test is intended to diagnose the following:
- Wheels/tires
- Wheel speed sensors
- ABS module
- 4X4 control module
PINPOINT TEST F : DTC P1635
WARNING: When directed to drive the vehicle as part of this test, drive the vehicle on a hard surface in an area without traffic to prevent a crash. Failure to follow these instructions may result in personal injury.
NOTE: Carry out a thorough inspection and verification as outlined before carrying out this pinpoint test. Refer to Inspection and Verification. Four Wheel Drive (4WD) Systems
F1 CHECK THE RECENT TIRE USAGE
- Check with customer about recent tire usage or installation.
Has a tire been installed on the vehicle recently that was not originally supplied with the vehicle or has the mini spare been used?
Yes
INFORM the customer that tire size should not exceed OEM recommendations and that all 4 tires should be the same size and brand. CLEAR the DTCs. REPEAT the self-test.
No
GO to F2.
F2 CHECK TIRE SIZE AND BRAND
- Check the tire size and the brand of tire.
Are all 4 tires the same size and brand?
Yes
GO to F3.
No
INFORM the customer that tire size should not exceed OEM recommendations and that all 4 tires should be the same size and brand. INSTALL new tire(s) as necessary. CLEAR the DTCs. REPEAT the self-test.
F3 CHECK TIRE AIR PRESSURES
- Check the air pressure in all 4 tires.
Are all 4 tires at the recommended air pressure?
Yes
GO to F4.
No
ADJUST the tire air pressures. CLEAR the DTCs. REPEAT the self-test. INFORM the customer to maintain the correct tire air pressure.
F4 CHECK FOR CORRECT WHEEL SPEEDS
- Connect the scan tool.
- Enter the following diagnostic mode on the scan tool: DataLogger- 4X4 Control Module.
- While driving the vehicle at 48 km/h (30 mph), monitor the following wheel speed sensor PIDs:
- Left Front Wheel Speed Sensor (LF_WSPD)
- Left Rear Wheel Speed Sensor (LR_WSPD)
- Right Front Wheel Speed Sensor (RF_WSPD)
- Right Rear Wheel Speed Sensor (RR_WSPD)
Are all 4 wheel speeds within 2 km/h (1.2 mph) of each other?
Yes
GO to F5.
No
The ABS module is sending invalid wheel speed data to the 4X4 control module. REFER to Antilock Brakes / Traction Control Systems for additional ABS diagnosis.
F5 CHECK FOR CORRECT 4X4 CONTROL MODULE OPERATION
- Disconnect: 4X4 Control Module C281.
- Check for:
- corrosion.
- pushed-out pins.
- Connect the 4X4 control module and make sure it seats correctly.
- Operate the system and determine if the concern is still present.
Is the concern still present?
Yes
INSTALL a new 4X4 control module. REFER to 4X4 Control Module . CLEAR the DTCs. REPEAT the self-test.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test.