P0602 Fault Code in Land Rover: Causes, Symptoms, and Fixes

This code means the ECM/PCM (Engine/Powertrain Control Module) has detected an error in its software or calibration data. Essentially, the PCM either:
– Wasn’t programmed correctly,
– Lost its programming, or
– Has corrupted software.
It often comes up after PCM replacement if it wasn’t flashed with the correct vehicle-specific software.

Possible Causes

1. Improper PCM programming (incorrect or incomplete reflash)
2. Wrong PCM installed (not compatible with vehicle)
3. Software corruption (voltage spikes, interrupted update)
4. Low battery voltage during programming
5. Faulty PCM/ECM (internal memory failure)
6. Rare: wiring/ground issue affecting PCM programming circuit

Symptoms

1. Check Engine Light (CEL) ON
2. Engine may not start or may run poorly
3. Transmission may go into limp mode
4. Other communication codes may appear (CAN bus errors)
5. Inconsistent drivability issues (stalling, hesitation, poor fuel economy)

Diagnosis & Fix

1. Check for PCM replacement history – was it recently swapped or reflashed?
2. Verify battery and charging system health – stable voltage is critical.
3. Inspect PCM wiring/grounds – ensure good connections.
4. If PCM was recently changed:
– Reprogram/reflash PCM with correct OEM software & calibration.
5. If PCM is original and suddenly shows this code:
– Software corruption → attempt a reflash.
– If reflash fails → PCM replacement required.