A vehicle’s ECU relies on a number of sensors to tell it what the vehicle is doing, and what gear the driver has selected. If the driving situation and gear selection do not meet preset parameters, a P0821 DTC will be set.
How Serious is the Code?
It’s important for the ECU to know what gear has been selected by the driver, so a P0821 diagnostic trouble code is rather important. Particularly if that ECU puts the transmission into limp load mode (it will be restricted to a single forward gear).
Symptoms of a P0821 include:
- Unusually hard shifts
- ‘Stuck’ in a gear
- Damaged wiring and/or connectors
- Misadjusted transmission range sensor
- Faulty transmission range sensor
How to Diagnose the Code?
One of the main causes of a P0821 OBDII trouble code is an electrical fault. So a mechanic should start by examining the condition of the wiring and connectors. If no problems are found, the transmission range sensor will need to be tested.
What Repairs Will Fix P0821?
- Repair or replace damaged wiring/connectors
- Adjust or replace transmission range sensor
- P0820 – Gear Lever X-Y Position Sensor Circuit
P0822 – Gear Lever Y Position Circuit
P0823 – Gear Lever X Position Circuit Intermittent
P0824 – Gear Lever Y Position Circuit Intermittent