For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### DTC Descriptor

DTC P0826: Up and Down Shift Switch Circuit

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Signal | P0826 | P0826 | P0826 | P0826
Low Reference | -- | P0826 | P0826 | P0826

### Typical Scan Tool Data

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: Ignition ON Parameter Normal Range: Not In Use, Shift Up, Shift Down
Signal | Not In Use | Not In Use | Not In Use
Low Reference | Not In Use | Not In Use | 1
1 Internal TCM damage may occur if shorted to B+

### Circuit/System Description

The shift/driver shift control allows the driver to shift gears by pushing the shift lever. Pushing forward on the shifter will command an upshift and pulling back will command a downshift. Ignition voltage flows from the ignition fuse through the switch resistor array to the transmission control module (TCM). The system is activated when the gear shift lever is in the D position and moved over into the shift/driver shift control gate area. When the shifter is moved over into the shift/driver shift control gate area, the up/down enable switch is closed and connects enable circuit from the body control module (BCM) to ground.

### Conditions for Running the DTC

#### P0826

• | The ignition voltage is between 10.2 V and 15.5 V.

• | The engine speed is greater than 400 RPM for 2 s.

• | The transmission is not in emergency mode.

• | Accessory ON for more than 3 s.

• | TCM communication is normal.

• | DTC U0140 is not set.

### Conditions for Setting the DTC

#### P0826

• | TCM receives up/down enable switch state is "illegal" for 4 s continuously.

• | TCM receives up/down switch state is "illegal" for 4 s continuously.

### Action Taken When the DTC Sets

#### P0826

• | DTC P0826 is a Type D DTC.

• | Inhibit manual shift mode, and go back to automatic mode.

### Conditions for Clearing the DTC

#### P0826

• | DTC P0826 is Type D DTC.

• | TCM receives up/down enable switch state is not "illegal" for 5 min continuously.

• | TCM receives up/down switch state is not "illegal" for 5 min continuously.

### Reference Information

#### Schematic Reference

Automatic Transmission Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Description and Operation

Transmission Component and System Description

Automatic Transmission Shift Lock Control Description and Operation

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

With the engine runs, engage the up and down switch positions while observing the Driver Shift Request scan tool parameter. The parameter should change to reflect the selected up or downshift switch position and with no up or downshift switch position selected the parameter should display None.

⇒ | If the parameter does not change to reflect the selected position, proceed to component testing.

### Component Testing

#### Static Test

1. Ignition OFF, remove the wiring harness connector from K71 Transmission Control Module (TCM).
2. Ignition ON shift lever in range D, test for 0.5-1.2 V between the low reference circuit terminal 3 (X2) and ground.

⇒ | If more than the specified range, test the circuit for short to voltage.

3. Shift lever in range shift/driver shift control, test for 1.3-1.6 V between the low reference circuit terminal 3 (X2) and ground while the shifter pushing forward for an upshift.

⇒ | If less than the specified range, test the circuit for short to ground or an open.

4. Shift lever in range shift/driver shift control, test for 2.5-3.6 V between the low reference circuit terminal 3 (X2) and ground while the shifter pushing backward for a downshift.

⇒ | If out of the specified range, test the circuit for short to ground, short to voltage or an open.

⇒ | If the test within specifications, replace the shift/driver shift control.

5. If all circuit test normal, replace K71 Transmission Control Module (TCM).

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Symptoms - Automatic Transmission Shift Lock Control

• | TCM, refer to Control Module References for replacement, setup and programming.

⇒ | Perform the Transmission Adaptive Functions.