Technical Description of OBD-II Trouble Code
Error in Control Module Programming
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code, which means it is applicable to OBD-II equipped vehicles (such as Dodge Ram Cummins, Chevy GMC Duramax, Isuzu, Volvo, Vauxhall, VW, etc.). Although it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.
Here is a photo of a PCM with the cover removed:
If your OBD II equipped vehicle has stored a code P0602, it means that the powertrain control module (PCM) has detected an internal programming error. The programming error applies to the PCM itself.
When you look at a PCM, you may only see a metal box, but what’s inside is crucial for efficient engine operation. Information vital to engine management is programmed from the factory using the electronically erasable programmable read-only memory (EEPROM).
Vehicle-specific settings for engine and transmission management are programmed into the EEPROM for each vehicle that leaves the factory. The EEPROM not only helps manage engine efficiency and performance, but also recognizes and interacts with other onboard vehicle control modules.
If the PCM detects inconsistencies with the EEPROM or fails to recognize the program of the EEPROM, a code P0602 will be stored and a malfunction indicator lamp (MIL) may illuminate. Depending on the severity of the malfunction, multiple ignition cycles (with a malfunction) may be necessary for MIL illumination.
Other internal control module error trouble codes include:
Code Severity & Symptoms
A stored code P0602 should be classified as severe because the conditions that caused it to be stored may significantly affect engine management.
Symptoms of a P0602 code may include:
Causes
Possible causes for this code include:
Diagnostic and Repair Procedures
Diagnosing a code P0602 can be challenging, even for the most experienced and well-equipped technician. However, there are a few preliminary tests that can be performed before giving up and seeking assistance from someone else.
As usual, I would start my diagnosis with a visual inspection of engine management wiring harnesses and connectors. Any damaged or burned wiring and connectors should be repaired or replaced. Next, I would connect the scanner to the vehicle diagnostic connector and retrieve all stored codes and freeze frame data. Before clearing the codes, I would write them down just in case this turns out to be an intermittent code. A code P0602 must be diagnosed and repaired before diagnosing and repairing any other stored codes, as other stored codes are likely to be false. Now, clear the codes in the hope that the P0602 has been stored in error.
If the P0602 is immediately reset, check for battery voltage to the PCM. The PCM requires battery voltage to function properly. If the battery terminals are corroded or loose, there may be inadequate voltage reaching the PCM. Check PCM relays and fuses for battery voltage with the circuit loaded. Corroded fuses may appear normal until a load is applied to the circuit and their deficiency is revealed.
Obviously, if the PCM has been recently replaced, there is a high likelihood that it was improperly programmed or not programmed at all. Also, a controller from another vehicle cannot be used unless it has been reprogrammed specifically for the vehicle in question, and aftermarket (high-performance) programmers may not be recognized by other controllers (especially initially), resulting in a P0602 being stored.
Incorrectly programmed or replaced controllers may be reprogrammed with a factory scanner. If you cannot access such a scanner, most dealerships offer PCM programming for a nominal fee. Some aftermarket PCM manufacturers offer preprogrammed controllers for certain models. Check with your auto parts supplier and have the vehicle identification number, mileage, and other relevant data available.
Additional diagnostic notes:
