P0862

What it means

P0862 is the generic SAE J2012 code for Gear Shift Control Module A Communication Circuit High. The engine or powertrain control unit monitors the communication link with the gear shift control module and has seen the circuit sitting at a higher voltage than expected, or has received invalid data over it. The exact module, wiring layout and whether it is a dedicated line or a network bus vary by model, so check the manufacturer data for the vehicle.

Symptoms

• Warning lamp on, such as the engine management or transmission warning light
• Gear selector not responding or gear position not shown correctly on the display
• Transmission stuck in a single gear or in limp mode
• Harsh, delayed or erratic gear changes
• Car refusing to start or move because the selector position cannot be confirmed
• Other warning lights or communication fault codes stored at the same time

Possible causes

• Damaged wiring, such as a circuit shorted to voltage, chafed or broken, between the control unit and the gear shift modulelikely
• Corroded, loose or water-damaged connector at the gear shift module or control unitlikely
• Low battery voltage or a poor power or earth supply to the gear shift modulepossible
• Faulty gear shift control module with an internal fault on its communication outputpossible
• Fault on the vehicle communication network that affects the link, depending on the model's network layoutpossible
• Faulty control unit or outdated software, where the manufacturer has issued a known update for this faultrare

How to diagnose

1. Read all stored codes and freeze frame data, noting whether other communication or transmission codes are present and whether the fault is current or intermittent
2. Check the battery condition and charging voltage, as low voltage can cause false communication faults
3. Inspect the gear shift module wiring and connectors for chafing, water ingress, corrosion, bent pins and poor terminal tension
4. Check fuses and the power and earth supplies to the gear shift module against the wiring diagram
5. Wiggle test the harness while watching live data or the fault status to find intermittent faults
6. With the circuits isolated and the ignition off, test the communication circuit for a short to voltage and for continuity against the manufacturer's wiring diagram
7. Check live data for selector position and module communication status, and compare against the expected values for the model
8. Check for technical service bulletins or software updates for this code on the vehicle

How to fix

• Repair or replace damaged wiring and fix any short to voltage on the communication circuit
• Clean, repair or replace corroded or damaged connectors and terminals
• Restore a good battery, power supply and earth connection to the module
• Replace the gear shift control module if testing confirms an internal fault, and carry out any programming or adaptation it needs
• Apply an official software update to the affected control unit only if the manufacturer lists it as a fix for this fault

Can I keep driving?

Nearby codes

• P0861GenericGear Shift Control Module A Communication Circuit Low
• P0863GenericTCM Communication Circuit