P0603 | p0603 internal control module comm error | code p0603 | p0603 obd2 | dtc p0603

P0603 | p0603 internal control module comm error | code p0603 | p0603 obd2 | dtc p0603

Hello friends welcome to the ig garage channel today I am telling you how to fix p0603 internal control module comm error so watch this video and learn how to fix it friends if you like this video then subscribe to the ig garage channel for more videos.

The P0603 code indicates that the Engine Control Module (ECM/PCM) has detected an error with its Keep Alive Memory (KAM). The KAM stores important adaptive data like fuel trims, idle settings, and transmission shift points, even when the ignition is off. If this memory is corrupted or loses power, the ECM cannot retain learned values.

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⚠ Symptoms:

Check Engine Light ON

Hard starting or no start condition

Rough idle or stalling

Poor acceleration or hesitation

Transmission shifting issues

Reduced fuel economy

🔍 Causes:

Weak or disconnected battery

Faulty or unstable alternator/charging system

Loose or corroded ECM power/ground connections

Faulty wiring harness or damaged connectors

Aftermarket ECU tuning or failed reprogramming

Defective ECM/PCM

🛠 Fixes:

Check and clean battery terminals & ground connections

Test alternator and charging system

Inspect wiring harness to ECM/PCM for damage

Reprogram/update ECM software

Replace ECM/PCM if fault persists

📍 Location:

The ECM/PCM is usually located in the engine bay (near fuse box or firewall) or under the dashboard depending on the vehicle.

💰 Repair Cost:

Battery/alternator service: $100 – $400

Wiring/connection repair: $50 – $200

ECM reprogramming: $100 – $300

ECM replacement: $500 – $1200+

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#P0603 #ECM #KeepAliveMemory #CheckEngineLight #OBD2Codes #IGGarage