Technical Description of OBD-II Trouble Code
Malfunction in the 5-6 Shift
This OBD-II powertrain code is considered generic because it applies to all vehicle makes and models (1996-newer). However, the specific repair steps may vary depending on the model.
What does that mean?
In vehicles with electronically controlled automatic transmissions, the 5-6 shift solenoid is responsible for activating the hydraulic circuits that change gears inside the transmission. The shift solenoids are controlled by either a Transmission Control Module (TCM) or the Engine Control Unit / Powertrain Control Module (ECU / PCM). The control circuit may be power or ground side controlled depending on the application.
Some vehicles self-test the circuit even when the gear is not in use. The 5-6 shift solenoid may be an on/off solenoid or duty cycle controlled. The PCM or TCM checks for an inductive kick to determine if the solenoid is functioning properly, even when not in use. This brief activation is too fast for the solenoid to actually cause a shift in the transmission. When the solenoid is activated and turned off, the magnetic field collapses, sending a slightly higher voltage to the PCM, which is used to determine if the solenoid is functioning properly. Note: This DTC is nearly identical to P0781, P0782, P0783, and P0784.
Symptoms
Symptoms of a P0829 DTC may include:
This condition may cause the check engine light to illuminate and possibly shut down the transmission controls altogether, resulting in a “failsafe” mode that will only allow one default gear depending on the vehicle’s state with all solenoids off.
Causes
Potential causes of a P0829 code include:
Possible Solutions
Disconnect the PCM or TCM wiring harness, depending on the application, and using an electrical diagram as reference, check for excessive resistance or an open in the control circuit. Using a Digital Volt Ohm Meter (DVOM) set to the Ohms scale, check for resistance on the 5-6 solenoid power and ground sources to determine if there is an open circuit or excessive resistance in the 5-6 solenoid. Visually inspect the harness connectors for any pinched, disconnected, or loose wires.
Short to power: Disconnect the battery positive cable and wiring harness connector at the transmission, and check for continuity using the DVOM between the power source and solenoid circuit wiring in the key on / engine off (KOEO) position, as well as the key off position.
Short to ground: Disconnect the battery positive cable and wiring harness connector at the transmission, and check for continuity using the DVOM between the 5-6 solenoid power source and a known good ground.
TCM or PCM failure: Using an advanced scan tool capable of controlling solenoids, manually activate the 5-6 shift solenoid. It may be necessary to manually activate the transmission control relay on some vehicles if power is not present at the transmission wiring harness connector. If a scan tool is not available, it will be necessary to monitor the 5-6 solenoid circuit to determine if the TCM or PCM is sending a power or ground signal to the 5-6 solenoid during vehicle operation.
