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Error Code P0819 is defined as Up and Down Shift Switch to Transmission Range Correlation. Error Code P0819 is a generic trouble code, meaning it applies to all vehicles with the OBD-II system, especially those made from 1996 up to present. This includes vehicles from, but not limited to, Audi, Ford, Honda, Hyundai, Kia, Lincoln, and Volkswagen. Specifications on the definition, troubleshooting, and repairs, of course, vary between make, model, and powertrain configuration.
If the vehicle stores the Error Code P0819, this means the PCM (powertrain control module) has determined a malfunction between the upshift/downshift switch, and the transmission range (shift range) switch. This code typically applies to vehicles with automatic transmission and paddle or sport shifters.
The TCM (transmission control module) used to be a standalone module, and now it’s part of the PCM. The upshift/downshift (paddle) shifter typically found on the steering wheel horn pad, close to the driver’s finger position. These sport shifters are usually found in high-performance cars. To ensure the gear selection is consistent with the upshift/downshift switch input signals, the PCM monitors the transmission range switch. Also, to ensure both remain in the set parameters, the PCM monitors the upshift/downshift switch and transmission range circuit voltage.
If the PCM determines the transmission gear selection is inconsistent with the gear selection signal input by the upshift/downshift switch, or if the circuit voltage is outside the allowable parameters, then it will set this error code while simultaneously illuminate the Check Engine light. In some cases, multiple ignition cycles (with a failure) may be needed to activate the Check Engine light.
- Disabled manual (paddle) upshift/downshift function
- Shift indicator shows the wrong gear
In other cases, the vehicle may not show symptoms at all.
- Faulty upshift/downshift switch
- Damaged transmission (shift) range sensor
- Shorted or open circuit in upshift/downshift or transmission range switch
- Faulty or programming error in the PCM
How to Check
You will also need a diagnostic scanner, DVOM (digital volt/ohmmeter), and a source of vehicle diagnostic information.
Use the vehicle’s information to find the TSB (technical service bulletin) that matches the specifics of the vehicle (make, model, engine size, symptoms, and codes stored). This could help for a more thorough diagnosis.
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 which contributed to the code being stored may need to worsen before an accurate diagnosis can be made.
If the code is immediately reset, the next step of your diagnosis will require that you search your vehicle information source for diagnostic flow-charts, connector pin-out charts, connector face views, and component testing procedures/specifications.
Test for the voltage, ground, and signal output at the right upshift/downshift and transmission range switch using the DVOM. Typically, the upshift/downshift switch circuits consists of either the battery voltage (activated) or the ground (deactivated)
Test the upshift/downshift and transmission range switches using the DVOM, make sure you refer with the source of vehicle diagnostic information. Switches that don’t test within system specifications must be replaced.
For fully functional system circuits, use the DVOM to test the upshift/downshift switch and transmission range switch circuits to the PCM or transmission. Make sure you disconnect all controllers before using the DVOM for testing.
How to Fix
- Replacement of the faulty upshift/downshift switch
- Repair or replacement of faulty wiring or damaged connectors for the switch
Error codes related to upshift/downshift to transmission range switch are usually caused by a switch failure.
This code indicates that there’s been a serious electrical problem or mechanical failure. Thus, this should be addressed as soon as possible.