Range Rover PCM Processor Fault (P0606): causes & how to fix it

As a long-time Range Rover owner, I’ve braved what has sometimes felt like the entire gamut of vehicle troubles. Sadly, the notorious PCM processor fault was one of them.

Join me as I share my insights, tips, and tricks to conquer and tame this fairly common Range Rover issue. Let’s get you back on the road!

What models are affected?

Signs and symptoms

The PCM (Powertrain Control Module) is responsible for managing the engine and transmission systems in your vehicle.

When it develops a fault, you may experience a range of problems such as:

  • Check Engine Light (CEL) illuminates: The CEL will typically stay on until the issue has been resolved.
  • Engine Misfiring: This occurs when the engine doesn’t run smoothly and performs poorly.
  • Poor Fuel Economy: A PCM fault can cause low gas mileage and a reduction in engine power.
  • Transmission Shifting Issues: You may encounter trouble shifting gears or slipping gears.
  • Stalling: The engine may shut off unexpectedly, causing a complete loss of power.

List of possible OBD codes

A PCM processor fault can cause many OBD (On-Board Diagnostics) codes to appear.

Here’s a list of some of the most common codes that are relevant to a PCM processor fault:

  • P0601 – Internal Control Module Memory Check Sum Error
  • P0602 – Control Module Programming Error
  • P0603 – Control Module Long-Term Memory Reset
  • P0604 – Control Module Random Access Memory Failure
  • P0605 – Control Module Programming Read-Only Memory (ROM) Error

It is essential to note that while these codes may indicate a PCM processor fault, they do not necessarily mean that it is the only cause of the issue.

Buying guide: Best Land Rover OBD2 scanner tools

Common causes

A PCM processor fault can occur for multiple reasons, some of which include:

  • Faulty Connections: This can be due to damaged, corroded, or loose connections between the PCM and the sensors or actuators.
  • Voltage Issues: A PCM needs a stable voltage supply to function correctly. If there’s too much or too little power, it can cause a fault.
  • Environmental Conditions: Extreme temperatures, moisture, or vibration can cause damage to the PCM and its components.
  • Software Failure: The software running on the PCM can become corrupted or outdated, causing a fault.

Can it be fixed without a mechanic?

Depending on the cause of the PCM processor fault, it may be possible to fix it without the help of a mechanic.

However, if you are unsure about an issue, it is always best to seek professional help.

Parts you’ll need to fix it

The parts you need to fix a PCM processor fault depend on the underlying cause of the issue.

Here are some components that could potentially be required:

  • PCM
  • Connectors
  • Wiring
  • Sensors (e.g., oxygen sensors, throttle position sensors)
  • Actuators (e.g., fuel injectors, ignition coils)

Tools you’ll need to fix it

Several tools will be essential for diagnosing and fixing a PCM processor fault.

Here is a list of some of the tools you may need:

  • OBD-II Scanner
  • Multimeter
  • Soldering Iron and Solder
  • Wire Strippers
  • Torx Driver Set
  • Socket Set
  • Electrical Tape
  • Zip Ties

How to fix it

Here is a step-by-step guide on how to fix a PCM processor fault:

1. Use an OBD-II scanner to retrieve Diagnostic Trouble Codes (DTCs) and identify the cause of the PCM processor fault.
2. Check all the fuses in the engine bay fuse box that are related to the PCM and replace any that are defective.
3. Check the wiring for any signs of damage, looseness, or corrosion and repair it accordingly.
4. Check the ground connections from the PCM to the engine block and make sure they are tight and free of corrosion.
5. Check the voltage at various points in the car’s electrical system to ensure that it is within the manufacturer’s specifications.
6. If the PCM is faulty, it needs to be replaced. This is a job for a professional mechanic or auto electrician.

Potential alternative causes

It’s essential to note that other issues may be causing the same symptoms as a faulty PCM processor.

Here are some alternative causes:

  • Faulty Fuel Pump: A faulty fuel pump may cause low pressure, resulting in engine stalling, misfiring, or power loss.
  • Bad Oxygen Sensor: A malfunctioning oxygen sensor causes incorrect air/fuel ratios, leading to poor gas mileage and idle quality.
  • Clogged or Dirty Fuel Injectors: Dirty or clogged fuel injectors can cause fuel to spray unevenly in the engine, leading to poor performance and gas mileage.


How expensive is it to replace a PCM processor?

The cost of replacing a PCM processor depends on the make and model of your car and whether you plan to do it yourself or hire a professional mechanic. This can range from $500 to $2,000.

Is it safe to drive with a PCM processor fault?

It’s essential to fix a PCM processor fault as soon as possible to prevent further damage to your vehicle. It’s not safe to drive with a malfunctioning PCM, as it can result in engine stalling or even a complete loss of power.

How long does it take to fix a PCM processor fault?

Fixing a PCM processor fault can take a few hours or a few days, depending on the root cause of the issue and the level of expertise of the mechanic doing the repair.


In conclusion, a PCM processor fault can cause a range of issues that can be frustrating to deal with. In this article, we have discussed how to identify, diagnose, and fix a PCM processor fault.

Remember that it’s essential to take the time and care to diagnose the issue correctly before attempting any repairs. With the right tools and expertise, you can get your vehicle back on the road in no time!

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