P0603 on 2007-2013 Chevrolet Avalanche: Keep Alive Memory (KAM) Error Causes and Fixes

What's Unique About the 2007-2013 Chevrolet AVALANCHE

On this generation of Chevrolet Avalanche and its GMT900 platform mates (Silverado, Tahoe, etc.), P0603 is not just an engine code. 🎬 Watch: A quick breakdown of what the P0603 code means. As noted in Technical Service Bulletin #PIP4653E, this code can also be stored in the Transmission Control Module (TCM). The TSB's main purpose is to guide technicians away from unnecessarily replacing the TCM, instead directing them to investigate power and ground issues first. Another TSB, #05-06-04-060A, highlights that this code can be shared across multiple modules, pointing to a general electrical system issue affecting more than just the main engine computer.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Check Engine Light is on
• Rough idle, especially on a cold start
• Hesitation during acceleration
• Decreased fuel economy
• Erratic or harsh transmission shifting
• Engine may be hard to start or stall intermittently
• ABS or Traction Control lights may also illuminate
• Driver Information Center (DIC) messages like 'Service StabiliTrak' or 'Service Traction Control' may appear

Most Likely Causes

1. Weak or Failing Battery 🔴 High Probability → Shop Vehicle Battery The Keep Alive Memory requires a constant, stable voltage. An aging battery that drops below the required voltage (typically ~12.4V) when the truck is off will cause the memory to be lost.
   How to confirm: Use a multimeter to test the battery. A healthy, fully charged battery should read above 12.4 volts with the engine off. With the engine running, the voltage should be between 13.7 and 14.7 volts, which indicates the alternator is charging correctly.
   Typical fix: Replace the vehicle's battery.
   Est. part cost: $150-$300
2. Loose or Corroded Battery Terminals/Cables 🔴 High Probability → Shop Vehicle Battery Vibration and exposure to the elements can cause battery connections to loosen or corrode over time, interrupting the power supply to the vehicle's modules. The design of the OEM terminal clamps on this platform has been noted by some owners as being prone to loosening.
   How to confirm: Visually inspect the battery terminals for white or greenish corrosion. Physically try to wiggle the battery cable clamps; they should not move.
   Typical fix: Disconnect the battery (negative terminal first), clean the posts and terminals with a wire brush and a baking soda/water solution, and securely retighten the clamps. Applying dielectric grease can prevent future corrosion.
   Est. part cost: $5-$20
3. Corroded or Loose Main Ground Straps 🟡 Medium Probability → Shop Engine Ground Strap GMT900 trucks are known for having issues with main ground straps, particularly the one from the engine block to the frame and the firewall ground straps. Corrosion or looseness at these points creates high resistance, causing intermittent and confusing electrical problems, including P0603.
   How to confirm: Visually inspect the braided ground straps. One key location is on the passenger side of the engine block, connecting to the frame. Another is on the firewall. Check for fraying, corrosion, or looseness. A voltage drop test across the ground strap can confirm high resistance.
   Typical fix: Remove, thoroughly clean the contact points and the strap end with a wire brush, and securely re-fasten. If the strap is heavily corroded or frayed, replace it.
   Est. part cost: $15-$50
4. Recent Battery Disconnection or Jump-Start 🟡 Medium Probability → Shop Vehicle Battery Any time the battery is disconnected for service or replacement, power to the KAM is cut, which will set a P0603 code. A jump-start can also cause a voltage spike or interruption that triggers the code.
   How to confirm: If the code appeared immediately after the battery was disconnected or the vehicle was jump-started, this is the likely cause.
   Typical fix: Clear the code with an OBD-II scanner. The code should not return if the power supply is now stable. The vehicle will relearn its adaptive settings over the next few drive cycles.
   Est. part cost: $0
5. Failing Alternator ⚪ Low Probability → Shop Alternator An alternator that is not producing a consistent voltage can cause the battery to drain or create electrical instability, leading to memory loss in the modules.
   How to confirm: With the engine running, test the battery voltage. If it's below 13.5 volts or fluctuating wildly, the alternator is likely failing.
   Typical fix: Replace the alternator.
   Est. part cost: $200-$450

Rare But Worth Checking

• Aftermarket Performance Tuner: If you have installed an aftermarket programmer or chip, it can sometimes interfere with the PCM's self-test procedures and set this code. Removing the tune and returning to the stock program will often resolve the issue.
• Improperly Installed Aftermarket Electronics: Poorly installed accessories like remote starters, alarms, or high-power audio systems can create a parasitic draw or interfere with the PCM's power supply, triggering a P0603. A parasitic draw test can help identify the offending circuit.
• Faulty Powertrain Control Module (PCM): → Shop Engine Control Module (ECM) While this is the component named in the code definition, it is rarely the actual cause. All other power and ground-related issues should be thoroughly ruled out before considering PCM replacement, as it is costly and requires programming.

Diagnosis Steps

1. Check for other DTCs. If other codes are present, address them first.
2. Inspect the battery terminals for corrosion and ensure the cable clamps are tight. Clean and tighten as needed.
3. With the engine off, use a multimeter to check battery voltage. It should be at least 12.4V.
4. Start the engine and check the charging system voltage at the battery. It should be between 13.7V and 14.7V.
5. If the battery and charging system test good, consider if the battery was recently disconnected. If so, clear the code with a scanner.
6. Inspect the main engine-to-frame and firewall ground straps for corrosion, damage, or looseness. These are known weak points on this platform.
7. Drive the vehicle for several cycles. If the code does not return, the issue was likely a temporary power loss.
8. If the code returns, perform a parasitic draw test to check for modules or accessories that are not shutting down correctly.
9. If an aftermarket tuner or remote start is installed, remove it and return the vehicle to its stock configuration to see if the code disappears.
10. If all other possibilities have been exhausted, the PCM or TCM may be faulty, which requires professional diagnosis.

Parts You'll Likely Need

• Battery (OEM #e.g., ACDelco Gold 94RAGM (Verify Group Size 94R or H7 for your specific vehicle)) — A weak or failing battery is the most frequent cause of the KAM losing power and triggering a P0603 code.
  Trusted brands: ACDelco, DieHard, Interstate
  OEM price range: $200-$350
  Aftermarket price range: $150-$300
• Battery Terminal Cleaners/Protectors — Ensuring a clean, solid connection at the battery is a primary and inexpensive fix for intermittent power issues.
  Trusted brands: NOCO, CRC
  OEM price range: $10-$25
  Aftermarket price range: $5-$20

Related Codes That Often Appear With This One

• P0601, P0604, P062F, P1621 — These are other internal control module error codes. The provided TSBs (#PIP4653E, #05-06-04-060A) state that P0603 can appear with these codes, indicating a potential module or widespread electrical issue.

Technical Service Bulletins (TSBs) & Recalls

• PIP4653E: Notes that DTCs P0601, P0603, P0604, P062F or P1621 can be stored in the Transmission Control Module and advises checking power/grounds before module replacement.
• 05-06-04-060A: Informs technicians that several DTCs, including P0603, can be shared in multiple modules, suggesting a systemic electrical issue.

Platform-Specific Known Issues

• Per TSB #PIP4653E, this code may be found in the Transmission Control Module (TCM), leading to shifting issues. The bulletin advises against replacing the TCM until all power and ground supply issues have been ruled out.
• TSB #05-06-04-060A indicates that P0603 is one of several control module codes that can be shared among different modules on the vehicle, pointing towards a general electrical fault rather than a specific component failure.
• Corroded or loose main ground straps are a well-documented issue on the GMT900 platform, often causing a variety of intermittent electrical faults, including P0603.

Mechanic-Grade Diagnostic Values

• Battery Voltage (Engine Off) — expected: >12.4 Volts. Failure: A reading below 12.4V indicates a discharged or failing battery that cannot maintain Keep Alive Memory.
• Charging System Voltage (Engine Running at Idle) — expected: 13.7 - 14.7 Volts. Failure: Voltage below 13.5V or fluctuating wildly suggests a failing alternator unable to supply stable power to the modules and battery.
• Voltage Drop Test (Grounds) — expected: < 0.2 Volts (200mV). Failure: A reading higher than 0.2V between the battery negative post and a ground point (e.g., engine block, firewall) indicates high resistance in the ground circuit, which can interrupt power to the PCM.

Scan Tool Commands That Help

• Tech 2 / GDS2 or equivalent professional scanner: Crankshaft Position (CKP) System Variation Learn (CASE Relearn) — This procedure is required after replacing the Powertrain Control Module (PCM). Failure to perform it may result in a separate trouble code (P0315) and incorrect misfire detection, even though it doesn't directly cause P0603.
• Tech 2 / GDS2 or equivalent professional scanner: Security Relearn / Theft Deterrent Relearn — This is mandatory after replacing the PCM to allow the new module to communicate with the vehicle's anti-theft system. Without this, the vehicle will not start.

Wiring & Ground Locations

• G103 — On the front of the passenger side (right side) cylinder head.. This is a primary ground location for the Engine Control Module (ECM). Corrosion or looseness at this specific point can directly interrupt the ECM's ground path, causing a P0603 code and other engine management issues.
• G104 / G108 — A braided ground strap running from the rear of the driver's side (left side) cylinder head (G104) to the firewall (G108).. This is the main ground connection for the vehicle's cab and body. A poor connection here can cause a cascade of seemingly unrelated electrical issues, including power interruptions to various modules that share body grounds, triggering a P0603.
• Main Battery Ground — The main negative battery cable connects to the engine block and/or the vehicle frame, typically near the radiator core support.. This is the foundation of the entire vehicle's ground system. Corrosion or looseness here will create a voltage drop across the entire electrical system, starving modules of consistent power and being a primary cause for the P0603 code.
• Underhood Fuse Block (UBEC) — Located in the engine compartment on the driver's side.. This block is the central power distribution point. The main power feeds for the PCM run through it. Internal corrosion from moisture can create high resistance or short circuits on the power supply pins for the PCM, causing a P0603.

Real Owner Repair Stories

• slow_restoration on YouTube / Forum Commenter (2007 Classic Silverado) — Intermittent door locking/unlocking stutter, a slew of codes including powertrain, O2 sensor heaters, and misfires.
  ❌ Tried (didn't work) Initial diagnosis pointed towards multiple separate failures.
  ✅ What actually fixed it The final fix was cleaning a corroded and loose frame ground connection. All other codes and symptoms disappeared after addressing the single bad ground.
• Reddit user in r/MechanicAdvice (2009 Chevy Silverado 4.8L) — Crank no start, driver front parking lights stay on constantly.
  ❌ Tried (didn't work) Initial checks before disassembling the fuse block.
  ✅ What actually fixed it The underhood fuse box had been pressure washed without its cover, causing severe internal corrosion. This blew the fuel pump control module fuse (causing the no-start) and shorted other circuits. The fix required replacing the entire underhood fuse block.
• Reddit user in r/G37 (2012 Infiniti G37 (Illustrates code behavior)) — A 'permanent' P0603 code was present on a scanner, but the Check Engine Light was NOT on.
  ❌ Tried (didn't work) Replaced battery., Replaced positive battery terminal with integrated fuses.
  ✅ What actually fixed it No fix was needed. It was determined that a 'permanent' DTC can remain in memory even after the fault is corrected (like a weak battery being replaced). As long as the vehicle runs fine and no active or pending codes are present, it does not indicate a current problem.

OEM Part Supersession History

• 12597121, 12612384, 12625455 → 12633238 (for many 2010+ applications) — Updates to hardware and internal logic for the E38 ECM platform.
  Heads up: While multiple service numbers exist for the E38 ECM, they are not always interchangeable. The correct part must be programmed with the vehicle's specific VIN and calibration file. Installing a replacement ECM requires a security relearn procedure and often a Crankshaft Position (CKP) System Variation Learn procedure using a professional scan tool.