• | 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. |
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
---|---|---|---|---|
Tap Up/Tap Down Switch Signal Circuit | 0 V | 0 V | 5-12 V | -- |
The driver shift control (DSC), also known as the TAP Shift, allows the driver to manually shift transmission modes and gears by pressing the Plus/Minus button and select the desired range of gears for your current driving conditions by using the DSC shift switch located on the automatic transmission gear shift lever. Pushing the Plus switch will command an upshift and pushing the Minus switch will command a downshift. 12 volt reference voltage flows from the ignition body control module (BCM) through the DSC switch resistor array to the BCM. The DSC shift system is activated when the gear selector is in the Manual (M) position. DSC system is deactivated in all other range positions.
• | The engine speed is between 500-6,500 RPM for at least 5 seconds. |
• | No DTC P0826. |
• | The vehicle speed is less than 200 km/h (124 mph) for 5 seconds. |
• | The transmission fluid temperature (TFT) is -59 to +159°C (-74 to +318°F). |
• | The system voltage is 11-18 volts. |
The BCM detects an upshift request for 3 seconds when the transmission range selector is in D or 600 seconds in P, R, or N.
The BCM detects a downshift request for 3 seconds when the transmission range selector is in D or 600 seconds in P, R, or N.
The BCM detects an invalid voltage on the TAP up/down signal circuit for 5 seconds.
• | P0815, P0816, and P0826 are Type C DTCs. |
• | The BCM disables TAP shift operation. |
P0815, P0816, and P0826 are Type B DTCs.
Automatic Transmission Controls Schematics
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Control Module References for scan tool information.
With the engine ON, engage the DSC Plus/Minus switch positions while observing the Driver Shift Request parameter in the body controls scan tool data list. 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 status changes from Upshift to Invalid, replace the DSC shift switch. |
⇒ | If the parameter status does not change, replace the BCM. |
⇒ | If the parameter status changes from Downshift to Invalid, replace the DSC shift switch. |
⇒ | If the parameter status does not change, replace the BCM. |
⇒ | If the circuits test OK, test the 12 volt reference circuit and the tap up and tap down signal circuit for an open or short to voltage. |
⇒ | If the resistance is not within specifications, replace the switch assembly. |
⇒ | If the resistance is within specifications, replace the BCM. |
Test the DSC shift switch for correct resistance value, 8.11-8.39 ohms.
⇒ | If the resistance is not within specifications, replace the DSC switch. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
• | Shift Lever Replacement for DSC shift switch replacement. |
• | Control Module References for BCM replacement, setup, and programming. |