Technical Description of OBD-II Trouble Code
Malfunction in the Control Circuit of the 1-4 Upshift (Skip Shift) Solenoid
What does that mean?
This diagnostic trouble code (DTC) is a generic powertrain code that applies to many OBD-II vehicles (1996-newer), including vehicles from Chevrolet, Mercedes-Benz, BMW, Ford, GMC, etc. The exact repair steps may vary depending on the year, make, model, and powertrain configuration.
If your vehicle has stored a code P0803, it means that the powertrain control module (PCM) has detected a malfunction in the transmission upshift (also called skip shift) solenoid control system.
The automatic transmission upshift control solenoid is used in vehicle applications where the transmission can be manually shifted through the gear range by pushing or pulling the shift lever in a singular direction. This feature is especially popular in high-performance or sports cars. An electronic solenoid is required to input a shift signal to the TCM and effect the desired gear change.
The transmission control module (TCM) may be a stand-alone unit but is most commonly integrated into a single housing with the engine control module (ECM), referred to as the PCM.
If the PCM detects a malfunction in the upshift solenoid control circuit, a code P0803 will be stored and a malfunction indicator lamp (MIL) will be illuminated.
What is the severity of this DTC?
A stored code P0803 indicates that a malfunction has been detected in the upshift solenoid control circuit. Since the upshift (or skip shift) system is an auxiliary or high-performance shifter feature, it is not a critical transmission control system, and a code P0803 should not be classified as severe.
What are some of the symptoms of the code?
Symptoms of a P0803 trouble code may include:
What are some of the common causes of the code?
Causes for this code may include:
What are some P0803 troubleshooting steps?
When diagnosing automatic transmission codes, you should start by ensuring that the transmission fluid is clean and filled to the appropriate level. If the fluid level is low, locate the source of the leak and repair it. Refill the transmission with the recommended fluid and proceed.
If the fluid is excessively dark and smells strongly of burnt friction material, it will need to be replaced. This can be done by removing the transmission pan (and draining the torque converter) or flushing the transmission (recommended). Replace the filter at this time as well. When removing the pan from the transmission, be careful to preserve any debris that may have landed therein. If the pan is relatively clear of debris, you can assume that the clutches are mechanically intact. If there is an excessive amount of friction material in the pan (and stuck to the magnet), the transmission will require a rebuild from a qualified technician.
To diagnose a code P0803, you will need a diagnostic scanner, a digital volt/ohmmeter (DVOM), and a source of vehicle-specific diagnostic information.
You can use your source of vehicle information to find a technical service bulletin (TSB) that matches the vehicle year, make, and model, as well as the engine size, stored code/s, and exhibited symptoms. If you find one, it could provide helpful diagnostic information.
With the transmission filled to the appropriate level with the recommended fluid, proceed with the first step of the diagnosis.
Step 1
Use the scanner (connected to the vehicle diagnostic connector) to retrieve all stored codes and pertinent freeze frame data. It is a good idea to write this information down before clearing the codes, then test-drive the vehicle until the PCM either enters readiness mode or the code is reset.
If the PCM enters readiness mode at this time, the code is intermittent and may be much more difficult to diagnose. If this is the case, the conditions that contributed to the code being stored may need to worsen before an accurate diagnosis can be made.
Step 2
If the code is immediately reset, the next step of your diagnosis will require you to search your vehicle information source for diagnostic flow-charts, connector pin-out charts, connector face views, and component testing procedures/specifications.
Step 3
Use the DVOM to test voltage and ground circuits at the skip shift solenoid. If voltage and ground are detected, use the DVOM to test the solenoid itself.
Step 4
If no skip shift components have failed, use the DVOM to test system circuits. The voltage drop testing method works well for this task. Disconnect all controllers from the circuit prior to testing resistance with the DVOM.
