Internal Control Module KAM Error
The P0603 code means the vehicle's onboard diagnostic system has detected: Internal Control Module KAM Error. This is a moderate severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- hard
- Estimated cost
- $20 - $1000 (parts and labor)
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Common Symptoms
- Check Engine Light illuminated
- Adaptive memory reset -- idle may fluctuate
- Radio presets and clock may reset
- Fuel trims return to default values
Probable Causes (Ranked by Likelihood)
- Battery disconnected or dead causing KAM loss Very High
- Loose or corroded battery cable High
- Failed KAM power supply circuit in ECM Moderate
- Parasitic draw draining the battery Low
Common Fixes by Vehicle
What techs usually find when diagnosing P0603 on specific vehicles — tap your vehicle for the fix and the exact part:
2003-2014 Chevrolet Tahoe/Suburban 5.3L Moderate DIY
PCM KAM (keep-alive memory) error on GM trucks is typically caused by a weak battery or intermittent power loss to the PCM. Load test the battery and check for voltage drop on the PCM power and ground circuits. If the battery and wiring are good but the code returns, the PCM has a failing internal memory chip. Note: this module must be programmed to your VIN before the car will run. A generic parts search returns blank or donor units, so order it through a dealer or a rebuilder that programs to your VIN, or have a shop flash it after installation.
Labor: 1-2 hours2004-2014 Ford F-150 5.4L/4.6L Easy DIY
The PCM KAM reset error on Ford trucks is often caused by a corroded battery cable terminal allowing momentary power drops. Clean both battery terminals and the negative ground cable at the engine block and body. Tighten all connections. Clear the code and monitor. If it returns, the PCM is failing.
Labor: 30 minutes - 1 hour2007-2015 Cadillac Escalade 6.2L Moderate DIY
Aftermarket remote start systems or alarm systems that interrupt PCM power cause P0603 on Cadillac Escalades. Check for aftermarket wiring tapped into the PCM power circuits. If an aftermarket system is installed, verify it is not causing voltage drops. Remove or properly wire the system if it is the cause. Note: this module must be programmed to your VIN before the car will run. A generic parts search returns blank or donor units, so order it through a dealer or a rebuilder that programs to your VIN, or have a shop flash it after installation.
Labor: 1-2 hoursFrequently Asked Questions
Can I drive with code P0603?
Yes, you can drive. Internal control module errors can cause unpredictable engine behavior.
Does P0603 mean I need a new ECM?
Not always. Some internal module errors can be resolved by reprogramming or reflashing the ECM with factory software. However, hardware failures (RAM, ROM, processor) typically require ECM replacement.
How much does an ECM replacement cost?
ECM replacement typically costs $300-$1500 including the part and programming. The ECM must be programmed with the correct calibration and vehicle options for your specific VIN.
Mechanics Guide Step-by-step diagnosis
Step-by-Step Diagnostic Procedure
-
Check battery condition and terminal connections -- clean and tighten as needed
-
Measure battery voltage with engine off -- should be above 12.4V
-
Check for parasitic electrical draw that may drain the battery
-
Clear the code and drive the vehicle through a complete drive cycle to relearn adaptive values
-
If the code returns with a good battery, the ECM KAM circuit may be faulty
Sources 2
This page is built from documented references. Verify against your own service info before repair work.
- SAE J2012Diagnostic Trouble Code Definitions (defines the generic OBD-II code ranges)
- Cross-checked against the SAE J2012:2002 DTC table (2026-08-27)archived scan of the SAE standard — readable copy, not SAE’s current edition
P0603 on Diesel, EV & Equipment
The same code ID appears across other engines and platforms. The diagnostic flow varies by manufacturer — these are the platform-specific breakdowns:
Commonly Affected Vehicles
- 2001-2013 Ford F-150
- 2003-2015 Ford Mustang
- 2002-2014 Ford Explorer
- 2004-2016 Ford Escape
Related Codes
See All Codes & Fixes for Your Vehicle
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