P0602 – Control Module Programming Error – iCarsoft Official Store

Last Updated: October 2025 | Applies to: All OBD-II vehicles including GM, Ford, Dodge, BMW, Mercedes-Benz, Toyota, and others.

🔍 What Does P0602 Mean?

The diagnostic trouble code P0602 indicates a Control Module Programming Error. It typically means the Powertrain Control Module (PCM) or Engine Control Module (ECM) has detected an internal configuration or software fault. This could happen after a module replacement, failed flash, or corrupted calibration data.

Many DIYers first encounter this issue when searching “P0602 PCM not programmed after replacement” or “how to reprogram ECU after P0602” — which we’ll cover step by step below.

⚠️ Common Symptoms of Code P0602

Check Engine Light illuminated immediately after starting the engine
P0602 code appears after replacing ECM or PCM
Hard start, no-start, or rough idle condition
Transmission shifting problems
Other communication codes such as U0100 or P0606 stored together

🔧 Common Causes of P0602

ECM/PCM not properly programmed or flashed for the vehicle
Corrupted software due to battery disconnect during reprogramming
Defective aftermarket or remanufactured PCM
Power or ground circuit interruptions to the control module
Wiring harness damage or poor connections
Voltage instability from faulty alternator or weak battery

iCarsoft CR Pro S Car Diagnostic Tool

In many cases, “P0602 code after replacing PCM” occurs when the new module hasn’t been programmed with the vehicle’s VIN or immobilizer data.

🧰 Step-by-Step Diagnosis Using iCarsoft CR PRO S

The iCarsoft CR PRO S is ideal for diagnosing P0602 Control Module Programming Errors, as it can read, clear, and display live data from the PCM, TCM, and BCM systems.

Scan for codes: Connect CR PRO S and perform a full system scan. Record all stored codes — often, P0602 appears with U-codes indicating lost communication.
Check module identification: Navigate to ECU Information on the CR PRO S. Confirm that the software version and VIN match your vehicle. If the VIN is blank or mismatched, the PCM is likely unprogrammed.
Verify power & grounds: Use the CR PRO S live data or a multimeter to confirm stable voltage between 13.5–14.8V. Overvoltage conditions (see related code P0563 System Voltage High) can cause flash corruption.
Inspect wiring harness: Check PCM connectors for bent pins, corrosion, or moisture. Wiggle test the harness while monitoring voltage drop.
Reflash or reprogram PCM: If software corruption is confirmed, reflash using OEM software tools (Ford IDS, GM SPS, etc.) or at a certified workshop.
Retest and verify: After reprogramming, clear codes with CR PRO S and confirm stable module communication.

📋 Real-World Examples

- A 2014 Dodge Ram owner reported P0602 after installing a reman PCM. Using the iCarsoft CR PRO S, they verified the module had no VIN programmed. After re-flashing the PCM with correct calibration, the code cleared permanently.

- A Mercedes-Benz C-Class exhibited both P0602 and P0563 after battery voltage spiked during charging. Voltage stabilization and ECU reprogramming resolved both issues.

These real-world cases match popular searches like “P0602 code won’t clear after ECU replacement” and “P0602 after battery disconnect”.

🧩 Quick Troubleshooting Tips

Always maintain stable battery voltage during ECU flashing — use a regulated power supply.
Check VIN and calibration IDs via CR PRO S; if mismatched, PCM must be reflashed.
Inspect alternator output — overvoltage can corrupt module memory.
Disconnect and reconnect all module connectors to clean minor oxidation.

❓ FAQ — Common Questions About P0602

Q: What does “Control Module Programming Error” mean exactly?

A: It means the PCM/ECM detected invalid or missing software calibration. This can happen when a module is replaced or when the reflash process was interrupted.

Q: Can I drive with code P0602?

A: In many cases, yes — but drivability may suffer. In some vehicles, it can cause no-start or limp mode. It’s best to diagnose as soon as possible.

Q: How do I fix P0602 after replacing PCM?

A: The replacement module must be programmed with your vehicle’s VIN, immobilizer, and calibration data. A professional scan tool or dealer service can do this. The iCarsoft CR PRO S can confirm if the VIN is missing and guide next steps.

Q: Could low or high voltage trigger P0602?

A: Yes. Unstable charging system voltage — as seen in “P0563 high voltage alternator test” cases — can corrupt module data during flash operations. Always verify charging stability before reprogramming.