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P0602 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.


P0602 is an OBD-II Code that refers to Control Module Programming Error


A P0602 code is caused by an ECM (Engine Control Module) receiving a signal that the Powertrain control module (PCM) has identified an internal programming mistake. The PCM itself has a fault.


Common causes for this code include:

  • A programming fault within the PCM
  • An open or shorted wiring harness connection to the PCM (Powertrain control module)
  • Faulty or damaged PCM 
  • Corroded, or damaged wiring harness
  • This may be due to a new incompatible PCM
  • Open or shorted wiring or connectors in the Control Area Network (CAN) harness
  • Insecure control module ground strap


The symptoms of a P0602 code are: 

Transmission-related problems include slipping, fault codes stored in the gearbox, and rough idling. In addition to these symptoms, cars with this stored code experience poor acceleration and a drop in fuel efficiency.


To diagnose a P0602 DTC code, a technician would:

1. Look for any loose connections or damage within the system. Check all wiring, connectors, and components for any loose connections or damage.

2. You may access any freeze frame data and stored trouble codes. This information might be useful when trying to establish the sequence in which the problem codes were recorded.

3. Clear the code and then drive the car to see whether the fault returns.

4. If the code reappears, use a specialized scanner, such as Autohex or Tech 2, to try and identify the reason for the code storage more quickly. Testing can also be time-consuming and expensive for the mechanic if it is not done correctly. The best results will be obtained when testing any circuitry while the car is in gear.

5. In case a probe is lost, best to install some sort of memory-saving gadget or risk having to reprogram the PCM and other control modules.

6. Then, using the digital volt/ohmmeter, test the continuity and ground of all control modules’ batteries.

7. Examine the continuity between the control modules in a CAN Bus system using a wiring diagram.

8. Lastly, clear the code and test to see if it returns.

Common mistakes

The following are common mistakes when diagnosing the trouble code P0602:

Reprogramming the control module in an attempt to fix the code

Replacing or repairing harnesses without checking their connections first for damage

Adding new components before making sure existing ones are working properly (the cause may be elsewhere) 

Treating all DTC codes as though they were equal when in fact different faults require different repair methods. 

Not using only genuine replacement parts when replacing parts that have been diagnosed by a technician with questionable diagnostic equipment or hard-to-handle scan tools.

The most common mistake is not clearing the trouble codes, which enables this and other related problems to recur quickly. Allowing stored trouble codes to remain unaddressed for extended periods of time can to more serious complications, including expensive

How serious is this?

A P0602 code is often considered by technicians to be the most serious of all. This is because it affects multiple systems (powertrain, body, and chassis controls, among others). If left unattended, this fault may lead to other problems in the car’s computerized control system.

What repairs can fix the code?

repair manuals

The following are solutions that may fix this problem:

  • Replacing the PCM, if necessary
  • Replacing damaged connector plug and corroded harness assemblies
  • After testing the individual control modules, replace any that are faulty.

Related codes

A P0602 is related to and may be accompanied by the following codes:

How much does it cost to fix the P0602 code?

The repair cost of a P0602 code varies depending on the type and amount of damage. Some technicians may charge a flat fee that can vary from $100 to $300; others prefer the billing method, where they charge by time and parts used. Other factors include:

  • Price of individual control modules (some may cost between $500 and $1,000) 
  • Labor rates in your region (average is between $75 and $120 per hour) 
  • Availability of genuine replacement parts at local auto-parts stores (pricing varies based on store location)


In conclusion, the P0602 code is one of the most serious trouble codes. It is often accompanied by other DTCs, which indicates there are several problems in the car’s computerized control system. The damage can be quite costly to repair depending on the cause and available replacement parts (some may cost up to $1,000). Fortunately, this code does not mean you need a new or remanufactured PCM; it often means that there is some corrosion in your engine wiring harness or corroded connections at the connector plug.

P0602 Code – What Does It Mean & How To Fix It