P0603 on 2007-2010 GMC Sierra 2500: Keep Alive Memory (KAM) Error Causes and Fixes

What's Unique About the 2007-2010 Gmc SIERRA 2500

For the GMT900 generation Sierra 2500, P0603 is often a system-wide electrical issue rather than a single failed computer. GM issued Technical Service Bulletins (TSBs) noting this code can appear in multiple modules simultaneously, advising technicians to diagnose power and ground issues before replacing expensive components. [⭐] The code is also particularly common on models with the Duramax diesel engine due to their high electrical demands and the frequent use of aftermarket performance tuners, both of which can cause voltage interruptions that trigger the code. Key ground 🎬 Watch: Understanding the P0603 code and its common causes locations, such as the braided strap from the firewall to the passenger-side cylinder head (G103), are known weak points for corrosion and looseness, directly causing this code.

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 illuminated
• Erratic or harsh transmission shifting
• Rough idle or engine stalling
• Reduced fuel economy
• Engine may be hard to start or crank slowly
• ABS or Traction Control light may also be illuminated
• Hesitation during acceleration

Most Likely Causes

1. Weak or Failing Battery 🔴 High Probability → Shop Vehicle Battery The Sierra 2500, especially with a Duramax diesel engine, has high electrical demands. A battery that cannot maintain stable voltage (above 10.5V) during engine cranking will cause modules to lose their keep-alive memory. Many owners report that a battery strong enough to start the truck can still be weak enough to set this code.
   How to confirm: Check the battery voltage with the engine off (should be ~12.6V). Perform a load test to check its health. Many auto parts stores offer free battery testing.
   Typical fix: Replace the vehicle's battery. Heavy-duty AGM batteries are recommended. Common sizes for this truck are BCI Group 48 (H6) or Group 94R (H7).
   Est. part cost: $175-$400
2. Loose or Corroded Battery Terminals and Grounds 🔴 High Probability → Shop Vehicle Battery Vibration and exposure to the elements can lead to loose connections or corrosion on battery posts and main ground straps. Key locations on GMT900 trucks include the braided strap from the firewall to the rear of the passenger-side cylinder head (G103) and the main ground on the rear driver's side of the engine block (G104).
   How to confirm: Visually inspect the battery terminals for white or blue-green corrosion. Physically attempt to twist the battery cable clamps; they should not move. Follow the main ground cables from the battery to the chassis and engine block, inspecting for tightness and corrosion, paying special attention to the firewall ground straps.
   Typical fix: Disconnect the battery, clean the terminals, cable ends, and ground contact points with a wire brush until shiny, and re-secure them tightly. Apply a dielectric grease or anti-corrosion spray.
   Est. part cost: $5-$20
3. Recent Battery Disconnection or Replacement 🟡 Medium Probability → Shop Vehicle Battery This is a normal occurrence. Any time the battery is disconnected for service, the keep-alive memory is lost by design, which will set a P0603 code.
   How to confirm: If the battery was recently replaced or disconnected for another repair, this is the almost certain cause.
   Typical fix: Clear the code with an OBD-II scanner. The code should not return during normal driving after the modules complete a drive cycle.
   Est. part cost: $0
4. Aftermarket Engine Programmer/Tuner 🟡 Medium Probability Common on diesel trucks, these devices reprogram the PCM. The process of flashing a new tune often involves a power cycle that can set a P0603 code as a normal byproduct. Some tuners can also cause software conflicts that trigger the code during normal operation.
   How to confirm: Check for the presence of an aftermarket tuner connected to the OBD-II port or evidence of a custom tune (e.g., stickers, aftermarket gauges).
   Typical fix: If no drivability issues are present, the code can often be cleared and ignored. If problems exist, returning the truck to its stock tune is a key diagnostic step.
   Est. part cost: $0
5. Failing Alternator / Charging System Issue ⚪ Low Probability → Shop Alternator A failing alternator can produce unstable voltage (spikes or drops), which can disrupt the PCM's memory and operation.
   How to confirm: With the engine running, check the voltage at the battery terminals. It should be stable, between 13.5 and 14.5 volts. Readings outside this range suggest a problem.
   Typical fix: Replace the alternator.
   Est. part cost: $200-$500

Rare But Worth Checking

• Faulty Powertrain or Transmission Control Module (PCM/TCM): → Shop Transmission Assembly This is rarely the cause. Before replacing a module, all power and ground circuits must be meticulously tested. TSB #05-06-04-060A specifically warns against premature module replacement. [⭐] TSB #PIP4653E suggests that if the code is isolated to the TCM, a software reprogram should be attempted before replacement. [⭐]
• Blown Fuse or Damaged Wiring: A blown fuse for the PCM/TCM constant power circuit or a damaged wire in that circuit can cause P0603. This requires checking the fuse box (UBEC) and performing a voltage drop test on the relevant power and ground wires to the module. The underhood fuse block itself can corrode internally.
• Improperly Installed Aftermarket Accessories: Accessories like remote starters, alarms, or high-power stereos that are improperly wired can cause a parasitic draw or voltage drop, triggering P0603. A forum user reported a poorly installed remote start tapping into a PCM power source was the root cause of their P0603 issue.

Diagnosis Steps

1. Check if the battery has been recently disconnected or replaced. If yes, clear the code and test drive to see if it returns. This is a normal occurrence.
2. Perform a complete battery and charging system test. Use a multimeter to ensure battery voltage is ~12.6V (engine off) and alternator output is stable between 13.5-14.5V (engine running). Have the battery load-tested.
3. Thoroughly inspect and clean the battery terminals and cable ends.
4. Inspect, clean, and tighten critical ground connections. Pay special attention to the negative battery cable-to-chassis connection and the braided ground straps from the firewall to the engine block (specifically G103 on the passenger side).
5. Inspect fuses related to the PCM and TCM constant power supply in the underhood fuse block.
6. If an aftermarket tuner is installed, return the vehicle to its stock programming. Clear the codes and re-test.
7. Use a professional scan tool to determine WHICH module set the code (PCM or TCM). This is critical for diagnosis. If symptoms are transmission-related, suspect the TCM. [⭐]
8. If the code persists, use a multimeter to check for correct voltage and good ground directly at the PCM/TCM connectors. A wiring diagram is necessary for this step.
9. Only if all other steps fail to identify a cause, and especially if other internal module codes (like P0601) 🎬 See this guide on fixing GM truck electrical and ground issues are present, should the control module itself be considered faulty.

Parts You'll Likely Need

• Vehicle Battery (OEM #ACDelco Gold 94RAGM (Group 94R/H7) or 48AGM (Group 48/H6)) — A weak or failing battery is the number one cause of P0603 due to voltage drops during cranking.
  Trusted brands: ACDelco, Interstate, Optima
  OEM price range: $250-$400
  Aftermarket price range: $175-$300
• Battery Terminal Cleaner and Protector Kit — Fixing poor electrical connections at the battery is a very common and inexpensive fix for intermittent power loss.
  Trusted brands: CRC, NOCO
  OEM price range: $10-$20
  Aftermarket price range: $5-$15

Related Codes That Often Appear With This One

• P0601 — This code indicates an internal memory checksum error. If seen with P0603, it more strongly suggests a failing control module. Both are mentioned in TSB #PIP4653E. [⭐, 8]
• P0604 — This code indicates an internal RAM error. Like P0601, its presence alongside P0603 points more directly to a module fault and is also listed in TSB #PIP4653E. [⭐, 8]
• P0700 — This is a general transmission fault code requested by the TCM. If P0603 is set in the TCM, it will often be accompanied by P0700 to illuminate the Check Engine Light.
• P062F, P1621 — These are also module programming or memory-related codes. Seeing them together with P0603 reinforces the TSB guidance that a systemic electrical or module issue may be present. [⭐]

Technical Service Bulletins (TSBs) & Recalls

• PIP4653E: DTCs P0601, P0603, P0604, P062F or P1621 Stored In The TCM. Advises identifying which module set the code and suggests reprogramming the TCM if the fault is isolated there.
• 05-06-04-060A: Informational bulletin on multiple shared control module DTCs (including P0603), warning against premature module replacement and advising careful diagnosis of the root cause.

Platform-Specific Known Issues

• GM Technical Service Bulletin #05-06-04-060A notes that P0603 is one of several DTCs that can be shared across multiple control modules, cautioning against immediate module replacement.
• GM Technical Service Bulletin #PIP4653E points out that P0603 may be found specifically in the Transmission Control Module (TCM), causing shifting concerns. It advises checking which module set the code and suggests reprogramming the TCM may be a valid repair step.
• Poor ground connections are a known issue. Specifically, the braided ground strap from the firewall to the passenger-side cylinder head (G103) is a common point of failure due to corrosion, leading to various electrical faults including P0603.

Mechanic-Grade Diagnostic Values

• PCM/ECM Keep Alive Memory Power Pin Voltage — expected: Battery Voltage (~12.6V with key off). Failure: Voltage less than 12.4V or any significant voltage drop indicates a wiring or fuse block issue.
• TCM (T43) Battery Power Pin Voltage — expected: Battery Voltage (~12.6V with key off). Failure: Less than 12.4V indicates a problem in the power supply circuit.
• TCM (T43) Ignition Power Pin Voltage — expected: Battery Voltage (~12.6V with key on, engine off). Failure: 0V or significantly less than battery voltage points to an issue with the ignition switch, fuse, or wiring.
• PCM/TCM Ground Pin Voltage Drop — expected: < 100mV (0.1V). Failure: Voltage greater than 100mV indicates a poor ground connection, which can cause floating voltages and module resets.

Scan Tool Commands That Help

• Tech2 / GDS2: Reprogram/Program ECM/TCM — This function, used with a GM TIS2Web subscription, is required after replacing a control module or if a GM software update is available to fix known bugs that could cause memory errors. It is also used to correct issues if an incompatible tune was flashed.
• Tech2 / GDS2: Idle Relearn Procedure / Transmission Adaptive Pressure Relearn — After power has been restored and the P0603 code is cleared, the KAM is empty. These functions can initiate or monitor the relearn process to restore a smooth idle and proper shift quality more quickly than a standard drive cycle.

Wiring & Ground Locations

• G103 — On the front or rear of the passenger side cylinder head.. This is a primary engine-to-chassis ground point. Corrosion or looseness here is a very common cause of unstable ground reference for the PCM/TCM, leading to P0603.
• G104 — At the left rear (driver's side) corner of the engine, on the cylinder head.. This is the attachment point for the main ground strap that connects the engine to the firewall (G108). A bad connection here directly impacts the control modules' ground path.
• G108 — On the firewall, in the driver's side rear corner of the engine compartment.. This is the termination point for the ground strap from G104, completing the critical engine-to-body ground circuit. Corrosion is common at this firewall stud.
• Underhood Fuse Block (UBEC) — Driver's side of the engine bay.. Contains the fuses (e.g., ECM BATT, TCM BATT) that supply constant power for the Keep Alive Memory. Internal corrosion from water intrusion can cause high resistance and interrupt this power supply.
• PCM Connector X1, Pin 20 — On the E38 PCM, located in the left front of the engine compartment. Pin 20 is a Red/White wire.. This specific pin provides the constant battery voltage feed required for the PCM's Keep Alive Memory. A fault in this wire or its circuit will directly cause P0603.
• TCM Connector (T43), Pins 1, 4, 12 — The T43 TCM is mounted on the transmission. The connector is a 16-pin connector.. Pins 1 and 4 (Red/Wht) provide constant battery power, while Pin 12 (Pnk) provides switched ignition power. A loss of voltage on any of these pins due to a broken wire or poor pin connection can trigger P0603 in the TCM.

Real Owner Repair Stories

• GM-Trucks.com forum user (2011 GMC Sierra 1500 (Similar GMT900 platform)) — Check engine light with P0603, aftermarket remote start was not working.
  ❌ Tried (didn't work) Clearing the code (it returned immediately), Checking battery and alternator (both tested good)
  ✅ What actually fixed it The owner discovered a faulty aftermarket remote start system had been poorly installed. A power wire for the remote start module was tapped into a critical PCM power source, causing a voltage drain. Removing the remote start system and repairing the spliced wire permanently resolved the P0603 code.

OEM Part Supersession History

• e.g., 12597121 (2007 E38 ECM) → e.g., 12612384 (2008 E38 ECM) — Internal hardware and operating system changes throughout the production run.
  Heads up: Flashing an E38 ECM with a calibration file from an incompatible year (e.g., writing a 2010 file to a 2007 ECM) can corrupt the module's boot sector and render it unresponsive ('bricked'). The Service Number (SERV#) on the module should be matched to the vehicle's year and model before attempting to reprogram with a different operating system.

Model Year Variations Within This Range

• 2007.5-2010: The 2007.5 model year marked the introduction of the LMM Duramax engine paired with the 6-speed Allison transmission, which uses the T43 Transmission Control Module (TCM). This module is external to the transmission, unlike some earlier designs. P0603 issues related to shifting point specifically to this T43 TCM or its wiring.