P0602: Control Module Programming Error (Meaning, Causes, Fixes)

What P0602 means

The powertrain control module (PCM) is the computer that runs the fuel, ignition and, on many vehicles, transmission systems. OBD-Codes.com explains that the vehicle-specific settings for the engine and transmission are programmed at the factory into the PCM's EEPROM (electronically erasable programmable read only memory), which also lets the PCM recognize and work with the vehicle's other control modules. If the PCM detects inconsistencies with that memory or can't recognize its program, it stores P0602. RepairPal describes it a little differently: the PCM regularly runs a self-diagnosis in which it performs normal calculations, and if the results aren't what it expects it sets P0602. The code is generic to OBD-II vehicles, but repair steps vary by make and model. OBD-Codes.com names Dodge Ram Cummins, Chevy and GMC Duramax, Isuzu, Volvo, Vauxhall and VW among the vehicles it applies to, and search interest shows people look it up most for Chevrolet (including the Silverado), Dodge Cummins, Ford (including the 6.7 Powerstroke) and Jeep, so check technical service bulletins (TSBs) for your vehicle.

Severity: can I keep driving?

Stop and fix promptly

Get it checked right away. RepairPal rates P0602 'Urgent', meaning it can cause severe damage or put people at risk, and OBD-Codes.com says it should be treated as severe because the problem behind it can affect how the engine is managed in a major way. Both sources list stalling and no-start among the symptoms. If the engine stalls, idles roughly or the transmission shifts harshly, stop driving and have it towed rather than risk losing power in traffic.

Common symptoms

• Check engine light on (OBD-Codes.com says it may take several drive cycles with the fault before the light comes on)
• Engine won't start
• Engine stalls or idles roughly
• Decreased engine performance and drivability problems
• Harsh or erratic automatic transmission shifting (OBD-Codes.com)
• Lower fuel economy (OBD-Codes.com)

Likely causes

Roughly most to least common, based on the sources below. Your vehicle may differ.

1. A PCM programming error (OBD-Codes.com)
2. A new or incorrect PCM, for example one from another vehicle that hasn't been programmed for yours (OBD-Codes.com)
3. An aftermarket (high-performance) PCM program or tuner installed (OBD-Codes.com)
4. A blown ECM/PCM fuse or bad PCM power supply relay (OBD-Codes.com)
5. A failed PCM (both sources)
6. Open or shorted wiring or connectors, including the CAN (control module network) harness (both sources mention wiring)
7. A loose control module ground strap or broken ground wire (OBD-Codes.com)

Diagnostic steps you can do

1. Read all stored codes and freeze frame data and write them down. OBD-Codes.com says to deal with P0602 first, because other codes stored with it are likely to be false.
2. Think about recent work: OBD-Codes.com says that if the PCM was recently replaced, there's a good chance it was programmed wrong or not at all, and a recently installed performance tuner can also set the code.
3. Look over the engine wiring harnesses and connectors for damage or burned spots.
4. Check that the battery terminals are clean and tight, since OBD-Codes.com says loose or corroded terminals can leave the PCM short of voltage.
5. Check the PCM fuses and power relay, and look for a loose or broken ground strap or wire.
6. Clear the code and see if it comes back. If it resets right away, the PCM's power supply and programming are the next things to check.

Typical fixes

• Repair damaged wiring, connectors or ground connections
• Replace a blown PCM fuse or bad PCM power relay
• Remove or update an aftermarket performance program, or reprogram the PCM back to the factory calibration
• Reprogram an incorrectly programmed or replacement PCM with a factory-level scan tool, which OBD-Codes.com says most dealers can do
• Replace and program the PCM if it has failed

Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.

Related codes

• P0601 Internal Control Module Memory Check Sum Error
• P0603 Internal Control Module Keep Alive Memory (KAM) Error
• P0604 Internal Control Module Random Access Memory (RAM) Error
• P0605 Internal Control Module Read Only Memory (ROM) Error
• P0606 Control Module Processor Fault (PCM/ECM Processor)

Also listed in this guide:

All Computer & output circuit codes (P06xx) →

FAQs

Sources

1. OBD-Codes.com: P0602 Control Module Programming Error
2. RepairPal: P0602 Control Module Programming Error (rated Urgent)