Mercedes-Benz Low-Range Light Flashes, Code P1831 – UnderhoodService

Mercedes-Benz Low-Range Light Flashes, Code P1831

If you receive customer reports on an applied vehicle of the low- range light flashing rapidly (18 times) after vehicle start with fault code P1831 (Positioner motor, position sensor or power supply is faulty) in the transfer case ECU, do not replace the transfer case motor.

If you receive customer reports on an applied vehicle of the low- range light flashing rapidly (18 times) after vehicle start with fault code P1831 (Positioner motor, position sensor or power supply is faulty) in the transfer case ECU, do not replace the transfer case motor. This is caused by temporary loss of communication between the transfer case control module and the shift motor position sensor.

Affected Models:
163.154/157/
174/175, as of Chassis # A346835.
To resolve, read out the fault codes and cycle the transfer case shift motor by following the below procedure.

Service Procedure:
1. Read out and erase the fault codes.
2. If fault codes other than P1831 are present, diagnose and repair accordingly (use appropriate damage code, operation code and time).
3. If fault code P1831 is present, start the vehicle.
4. Shift the transmission into neutral (N).
5. Push the LOW RANGE switch. Depress the brake pedal.
6. After the shift motor has cycled, push the LOW RANGE switch again. The LOW RANGE light should go out at this time.
7. Confirm proper transfer case shift function: Cycle ignition and repeat steps 2-5.
Warning: While performing the transfer case shift adaptation described above, take all necessary safety measures, such as applying the parking brake and firmly holding the service brake. (Failure to do so can result in unintended vehicle movement.)

Courtesy of IDENTIFIX.

You May Also Like

Alternator Testing For No Charge Conditions

Many alternator problems turn out to be nothing more than a bad connection at the alternator or a bad wiring harness.

If only battery voltage is present at the battery on a running engine, does this mean the alternator is “bad?” No, it does not. It only means that the alternator is not charging, but does not reveal why. Therefore, it does not point to a faulty alternator. All too often, the alternator is condemned by technicians due to this test alone. The cause could instead be a module that distributes the power to the vehicle and regulates the alternator.

Understanding Coolants

All-season coolant used inorganic acid technology and worked great for almost 30 years.

Ignition System Do’s and Don’ts

Why do ignition systems give technicians problems when diagnosing ignition-related misfires? The answer is that some technicians use tests that might give inconclusive results or do damage to the coil or drivers inside a module.

Tools To Service Serpentine Belts

Servicing the serpentine belt on some vehicles is a tough task.

Battery Charging and Diagnostics

Here are six tips to use when diagnosing a vehicle with a dead battery. 

Other Posts

Hybrid Vehicle Fluid Maintenance

There are opportunities your shop can’t pass up just because the car or SUV has a hybrid badge on the back.

Using a Scope

Ignition coil and plug diagnostics.

Scope-diagnostics
Repairing Wiring Harnesses

A guide to probing and poking.

Diagnostic Procedures For Stop/Start Systems

Stop/start technology is more than just a switch wired to the brake pedal and starter.