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 Descriptors
DTC P0815: Upshift Switch CircuitDTC P0816: Downshift Switch Circuit
DTC P0826: Up and Down Shift Switch Circuit
DTC P1876: Up and Down Shift Enable Switch Circuit Low Voltage
Diagnostic Fault Information
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 | -- |
Circuit/System Description
The range selection mode (RSM), also known as the TAP Shift, allows the driver to manually shift gears by pressing the Plus/Minus button and select the desired range of gears for current driving conditions by using the RSM 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. A 12-volt reference voltage flows from the body control module (BCM) through the RSM switch resistor array to the BCM. The RSM shift system is activated when the gear selector is in the Manual (M) position. RSM system is deactivated in all other range positions.
Conditions for Running the DTC
The engine speed is between 500-6,500 RPM for at least 5 seconds.
P0815 or P0816
| • | No DTC P0826. |
| • | No DTCs P1815 or P1826. |
| • | The time since the last gear selector range change is greater than 6 seconds. |
P1876
| • | No DTC U0100. |
| • | No DTCs P0815, P0816, or P0826. |
| • | No DTCs P1825 or P1915. |
Conditions for Setting the DTC
P0815
The BCM detects an upshift request for 3 seconds in PARK, REVERSE, NEUTRAL, or D6 and for 600 seconds in PARK, REVERSE, NEUTRAL, D2, D4, OR D6.
P0816
The BCM detects a downshift request for 3 seconds in PARK, REVERSE, NEUTRAL, or D6 and for 600 seconds in PARK, REVERSE, NEUTRAL, D2, D4, or D6.
P0826
The BCM detects an invalid voltage on the TAP up/down signal circuit for 5 seconds.
P1876
The BCM detects a TAP Enable Switch request 3 times when not in M (D6) range for 2 seconds.
Action Taken When the DTC Sets
| • | DTCs P0815, P0816, P0826, and P1876 are Type C DTCs. |
| • | The BCM disables TAP shift operation. |
Conditions for Clearing the DTC
DTCs P0815, P0816, P0826, and P1876 are Type C DTCs.
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics
Connector End View Reference
DTC Type Reference
Electrical Information Reference
Circuit/System Verification
P0815, P0816, or P0826
With the engine ON, engage the RSM 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.
P1876
With the engine ON, move the transmission range selector from the Park (P) range to the Drive (D) range and over into the RSM gate while observing the Tap Up/Down Enable parameter on the scan tool in Body and Accessories/Instrument Panel scan tool data list. The parameter should display Enabled when in the RSM gate area, and Disabled in all other ranges.
| ⇒ | If the parameter does not change when the transmission range selector is in the RSM gate, proceed to Circuit/System Testing. |
Circuit/System Testing
P0815
- Select the Driver Shift Request parameter.
- Disconnect the automatic transmission RSM shift switch connector.
| ⇒ | If the parameter status changes from Upshift to Invalid, replace the RSM shift switch. |
| ⇒ | If the parameter status does not change, replace the BCM. |
P0816
- Select the Driver Shift Request parameter.
- Disconnect the RSM shift switch connector.
| ⇒ | If the parameter status changes from Downshift to Invalid, replace the RSM shift switch. |
| ⇒ | If the parameter status does not change, replace the BCM. |
P0826
- Test the 12-volt reference circuit and the tap up and tap down switch signal circuit for a short to ground.
- Test the RSM shift switch for correct resistance value, 8.11-8.39 ohms.
| ⇒ | 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. |
P1876
Key On, engine Off, in PARK, disconnect the Tap Up/Tap Down Enable Switch connector from the switch. Using a scan tool, observe the Tap Up/Down Enable parameter in Body and Accessories/Instrument Panel scan tool data list. The parameter should display Disabled.
| ⇒ | If the parameter does not display Disabled while disconnected, test the Tap Up/Tap Down Enable signal circuit for a short to ground. If no short to ground is found, replace the BCM. |
| ⇒ | If the parameter displays Disabled when disconnected and Enabled when connected, ensure the mechanical enable switch linkage is not bent, binding, or damaged and if no concerns are found, replace the Tap Up/Tap Down Enable switch. |
| ⇒ | If the parameter displays Disabled at all times, test the Tap Up/Tap Down ground circuit for an open or short to voltage. |
Component Testing
Test the RSM shift switch for correct resistance value, 8.11-8.39 ohms.
| ⇒ | If the resistance is not within specifications, replace the RSM switch. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Replace the RSM shift switch. Refer to Shift Lever Replacement . |
| • | Replace the BCM. Refer to Control Module References for replacement, setup, and programming. |
