Error Code P0803 1-4 Upshift (Skip Shift) Solenoid Control Circuit Malfunction. It is a generic trouble code, meaning it applies to all vehicles with the OBD-II system, especially those made from 1996 up to present and equipped with automatic transmission. Specifications on the definition and steps for repairs may vary depending on the model and make of the vehicle.

This includes vehicles from, but not limited to, BMW, Chevrolet, Ford, GMC, and Mercedes-Benz. Specifications on the definition, troubleshooting, and repairs, of course, vary from one make and model and powertrain configuration.

If the vehicle stores the Error Code P0803, this means the PCM (powertrain control module) has determined a malfunction in the transmission upshift (also referred to as skip shift) solenoid control system.

The automatic transmission upshift control solenoid is used for vehicles where the transmission can be manually shifted using the gear range by either pushing or pulling the shift lever in a singular direction. This is especially common among high-performance cars or sports cars. Since the shifter only needs to be slightly moved, the electronic solenoid is required to input a shift signal to the PCM and effect the desired gear range.

The TCM (transmission control module) and TCCS may be stand-alone units, but they are commonly integrated into a single housing with the ECM (engine control module), and this is what is usually referred to as PCM.

If the PCM determines a malfunction in the upshift solenoid control circuit, then this code will appear and simultaneously activate the malfunction indicator lamp (MIL).

Common Symptoms

  • Partially or totally disabled skip shift
  • Skip shift indicator lamp is flashing or activated
  • The transmission may be in limp-mode

Possible Causes

  • Faulty skip shift solenoid
  • Shorted or open skip shift solenoid control connectors or wirings
  • A programming error in the controller

How to Check

Before diagnosing this code, make sure the fluid is clean, and the transfer case is filled to the appropriate level. If there is not enough fluid (level too low), then there must be a leak. Find the source of the leak and do the necessary repair. Then, refill the transfer case with the require fluid before proceeding with the diagnosis.

If the fluid is dark and smells strong of burnt friction material, then it must be completely replaced. You can remove the transmission pan to drain the torque converter or flush the transmission (recommended). You need to replace the filter as well.

When removing the pan from the transmission, preserve whatever debris may have landed therein. If the pan is clear of debris, then you can assume that the clutches are still mechanically intact. If there’s a lot of friction material present in your pant (and stuck to the magnet), you will have to take the vehicle to a qualified technician to rebuild the transmission.

First Step

Retrieve all stored codes and the pertinent freeze frame data by connecting the diagnostic scanner. You can write the information down before clearing the codes and take the vehicle for a test-drive until the PCM either enters readiness mode or the code is reset.

If the PCM sets to readiness mode, the code must be intermittent. This can be more difficult to diagnose, as the condition that caused the code may need to worsen before you can proceed with the diagnosis.

Second Step

If the code immediately resets, however, then you can get to the next step. Read your vehicle information source and familiarize yourself with the diagnostic flow-chart. Locate the connector pin-out charts, connector face views, and the specifications for the component testing procedures.

Third Step

Test the voltage and ground circuits at the TCCS controller by using the DVOM. If you can detect both voltage and ground, use the DVOM to check the controller output. Test the components and sensors related to the specific symptoms. Any components that fail to comply with the recommended specifications are probably defective.

Fourth Step

If the TCCS components are in good condition, then test the system circuits using the DVOM. You can use the voltage drop testing method for this step. Make sure you disconnect all controllers before testing for the resistance with your DVOM.

How to Fix

Common repairs for this code include:

  • Wiring replacement
  • Replacement of solenoid actuator or relay
  • Replacement of shift solenoid
  • Replacement of solenoid connector at the PCM

This code is a serious problem. If the conditions that contributed to this code are present, then it should be addressed as soon as possible.

To avoid misdiagnosis, test the skip shift control circuit fuses with the circuit loaded.