P0603 on 2007-2010 Pontiac G6: Keep Alive Memory (KAM) Error Causes and Fixes

What's Unique About the 2007-2010 Pontiac G6

On the Pontiac G6 and related GM Epsilon platforms (like the Chevy Malibu and Saturn Aura), P0603 has a specific history documented in Technical Service Bulletins (TSBs). TSB #PIP4653E explicitly notes that this code can be stored in the Transmission Control Module (TCM), not just the main engine computer. This is a key detail, as it means drivability issues like harsh shifting could be the primary symptom. Another bulletin, #05-06-04-060A, confirms that P0603 and other related module codes can be shared across multiple control units, sometimes making diagnosis confusing if you only check the engine computer. Furthermore, many G6 models have the battery located in the trunk, which means the power and ground cables are longer and have more potential failure points (corrosion, damage) along their length to the front of the car.

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
• Harsh or erratic transmission shifting
• Rough or unstable idle
• Engine may hesitate or stumble on acceleration
• Difficulty starting the engine, intermittent no-crank, or stalling
🎬 Watch: How to solve a G6 no-crank no-start condition
• Reduced fuel economy
• Illuminated ABS or Traction Control light
• Gauges on the dashboard may shut off and reset intermittently

Most Likely Causes

1. Weak, Failing, or Recently Disconnected Battery 🔴 High Probability → Shop Vehicle Battery This is the most common cause for a KAM error on any modern vehicle. The control modules are sensitive to voltage drops, which can occur during engine cranking with a weak battery or any time the battery is disconnected for service. On the G6, the battery is often in the trunk, but some models have it under the hood, so location varies.
   How to confirm: Use a multimeter to test the battery. A healthy battery should read above 12.4 volts with the engine off and 13.7-14.7 volts when running. A load test, often done for free at auto parts stores, is the most definitive way to confirm battery health.
   Typical fix: Replace the vehicle's battery. After replacement, the code may need to be cleared with a scan tool, though it may clear on its own after a few drive cycles.
   Est. part cost: $150-$250
2. Loose or Corroded Battery Terminals/Cables 🟡 Medium Probability → Shop Vehicle Battery Corrosion or loose connections interrupt the constant power supply required by the modules to maintain their keep-alive memory. This is a known issue on the G6, with owners reporting intermittent no-start conditions that are resolved by cleaning or replacing cable ends.
   How to confirm: Visually inspect the battery terminals for white or greenish corrosion. Physically attempt to twist the terminal clamps; they should not move. Inspect the ground cable connection to the chassis and engine block for tightness and corrosion. A common failure point is the G105 ground splice on the transmission stud, which can corrode and break internally.
   Typical fix: Clean the battery posts and terminals with a wire brush and a baking soda solution. Ensure all connections are tight and secure. Replace corroded terminals or cables if necessary.
   Est. part cost: $5-$50
3. Failing Alternator / Charging System Issue ⚪ Low Probability → Shop Alternator An alternator that produces inconsistent voltage (too high or too low) can disrupt the modules and cause memory loss. In some G6s, a related issue is the failure of the fusible link cable that runs from the alternator to the starter, which prevents the battery from charging even with a good alternator.
   How to confirm: With the engine running, check the battery voltage with a multimeter. It should be stable, between 13.7 and 14.7 volts. If the voltage is fluctuating, low, or excessively high, the alternator is likely faulty. If the alternator tests good but the battery isn't charging, check for voltage at the alternator's main output post.
   Typical fix: Replace the alternator and serpentine belt. In some cases, the fusible link between the alternator and starter may need replacement.
   Est. part cost: $200-$400

Rare But Worth Checking

• Faulty Powertrain or Transmission Control Module (PCM/TCM): → Shop Transmission Assembly This is rare and should only be considered after all power supply issues have been exhaustively ruled out. The code indicates a memory *loss*, which is almost always caused by an external power problem, not an internal module failure.
• Wiring Issue in a Power or Ground Circuit: A damaged wire or a poor ground connection for the PCM or TCM can interrupt the keep-alive power supply. A known issue on the G6 platform is a bad ground splice (G105) under the throttle body on a transmission stud 🎬 Watch: How to diagnose G6 wiring and ground problems, which can cause a no-start and various electrical faults. Another potential failure point is a cracked solder joint inside the underhood fuse box, which can cause intermittent no-start conditions when hot.
• Faulty Fusible Link: A specific repair documented for a Pontiac G6 involved a failed fusible link located near the starter. This prevented the alternator from charging the battery, leading to a persistent low voltage condition and triggering P0603 even after replacing the alternator.

Diagnosis Steps

1. Check for other DTCs. If other codes are present, diagnose them first, as they may be the root cause.
2. Inspect the Battery and Terminals: Check the battery's state of charge. A healthy battery should be above 12.4V with the engine off. Clean any corrosion from the terminals and ensure the clamps are tight. Remember to check the battery in the trunk if it's not under the hood.
3. Test the Charging System: Start the engine and measure the voltage at the battery. It should be between 13.7V and 14.7V. If it's low, the alternator or its wiring (including the fusible link) may be faulty.
4. Inspect Main Ground Connections: Check the main battery ground cable connection to the vehicle's chassis and the engine-to-chassis ground strap. A critical ground point on the G6 is G105, located on a transmission stud under the throttle body; this splice is a known failure point.
5. Check for Parasitic Draw: If the battery repeatedly dies, perform a parasitic draw test to see if a component is draining power when the car is off. This can cause a low voltage state on startup, triggering P0603. An acceptable draw is typically under 50 milliamps (0.05A) after all modules have gone to sleep (wait 30-45 minutes).
6. Clear the Code and Perform a Drive Cycle: If the battery and charging system test okay, clear the P0603 code with a scanner. Drive the vehicle for 15-20 minutes to see if the code returns. If it was set due to a temporary power loss (like a battery disconnect), it may not come back.
7. Check for TSBs: As noted, TSB #PIP4653E specifically points to the TCM as a possible source 🎬 See this walkthrough on TCM location and replacement for this code on the G6 platform. If transmission symptoms are present, this is a strong possibility.
8. Advanced Diagnostics: If the code persists, a professional may need to perform a voltage drop test on the power and ground circuits for the PCM and TCM to find a potential wiring fault. In rare cases, a faulty underhood fuse block with internal cracks can cause these issues. Module replacement is a last resort.

Parts You'll Likely Need

• Automotive Battery (OEM #ACDelco Gold 90-6YR (Group 90) or T5-AGM (Group T5)) — This is the most frequent cause. An old or weak battery cannot maintain the stable voltage required by the control modules, causing them to lose their keep-alive memory.
  Trusted brands: ACDelco, DieHard, Duralast
  OEM price range: $200-$300
  Aftermarket price range: $150-$250
• Battery Terminals — Corroded or damaged terminals create resistance and prevent a solid electrical connection, which can mimic the effects of a weak battery and trigger a P0603 code.
  Trusted brands: Deka, Standard Motor Products
  OEM price range: $10-$30
  Aftermarket price range: $5-$20

Related Codes That Often Appear With This One

• P0601 — This is an 'Internal Control Module Memory Check Sum Error'. Both codes are mentioned together in GM TSBs #PIP4653E and #05-06-04-060A, indicating they can appear together due to general module or power supply issues.
• P0604 — This indicates an 'Internal Control Module Random Access Memory (RAM) Error'. Like P0603, it points to a memory fault within a module and is often triggered by the same power supply interruptions. It is also cited in TSB #PIP4653E.
• P1621 — This is a GM-specific code for 'Control Module Long Term Memory Performance'. It is directly related to P0603 and is also mentioned in TSBs #PIP4653E and #05-06-04-060A as a related module memory code.

Technical Service Bulletins (TSBs) & Recalls

• PIP4653E
• 05-06-04-060A

Platform-Specific Known Issues

• TSB #PIP4653E: This bulletin highlights that on some GM vehicles, including platforms related to the G6, DTCs P0601, P0603, P0604, P062F, or P1621 may be stored in the Transmission Control Module (TCM). This is critical because symptoms may be transmission-related, and a technician might mistakenly focus only on the engine computer.
• TSB #05-06-04-060A: This informational bulletin notes that P0603 is one of several control module DTCs that can be shared across multiple modules, reinforcing the idea that the issue may not be isolated to just the PCM.
• Faulty Ground Splice G105: A well-documented failure point is a multi-wire ground splice (G105) located on a transmission stud under the throttle body. The wires can corrode and break inside the crimp, leading to an open ground circuit that causes intermittent no-start conditions and various electrical codes, including P0603.
• Cracked Underhood Fuse Box: In some cases, particularly causing a no-start when the engine is hot, the underhood fuse panel can develop internal cracks on its circuit board. This interrupts power to critical components and can trigger KAM errors.

Mechanic-Grade Diagnostic Values

• ECM/PCM Keep Alive Memory (KAM) Power Supply Voltage — expected: Constant Battery Voltage (12.0V+). Failure: Voltage is 0V or significantly below battery voltage.
• TCM Power Supply Fuses — expected: Fuses should be intact and show battery voltage on both sides.. Failure: Blown fuse or corrosion in the fuse holder terminals.
• Parasitic Current Draw — expected: < 50 Milliamps (0.05 Amps). Failure: A sustained draw over 100 Milliamps (0.10 Amps) indicates a module or component is not shutting down correctly, which can drain the battery and cause a P0603 on startup.

Scan Tool Commands That Help

• GM Tech 2 / GDS2 with SPS: Service Programming System (SPS) — This function is required after replacing the Transmission Control Module (TCM). A new or used TCM must be programmed with the vehicle's specific VIN and the latest software to function correctly. An unprogrammed module will typically result in a no-start condition or persistent communication codes.

Wiring & Ground Locations

• G105 — On a transmission stud, on the left rear side of the engine compartment, often located under the throttle body assembly.. This is a critical shared ground point for both the Engine Control Module (ECM) and the Transmission Control Module (TCM). Corrosion or looseness here is a very common cause of intermittent power loss, communication codes (like U0101), and memory codes like P0603.
• ECM X1 Connector (Black) — The black connector of the two main connectors on the Engine Control Module, located in the engine bay.. Pin 20 (typically a Red/White wire) is the constant battery positive voltage feed for the Keep Alive Memory. A voltage drop or loss on this pin will directly cause a P0603.
• ECM X2 Connector (Gray) — The gray connector of the two main connectors on the Engine Control Module, located in the engine bay.. Pin 73 is a primary ground for the ECM. A poor connection here can contribute to various module errors, including memory faults.
• Underhood Fuse Block — Located in the engine bay, typically near the battery or strut tower.. This block contains the primary power fuses for the TCM (Fuse #4 and #42). Loose or corroded female terminals within the block can cause an intermittent power supply to the TCM, triggering P0603. Internal cracked solder joints are also a known failure on G6 models, causing intermittent electrical issues.

Real Owner Repair Stories

• Reddit user post (Vehicle unspecified, but common GM platform) — Car cranks but will not start, P0603 code is present.
  ❌ Tried (didn't work) Initially jumped the car and it ran, but stalled and would not restart.
  ✅ What actually fixed it The issue occurred after replacing the alternator without disconnecting the battery. The main starter wire was accidentally shorted, which blew the 120-amp main battery fuse. The P0603 was a direct result of this major power interruption and subsequent low voltage condition. The ultimate fix was to replace the main fuse and ensure all connections were secure.

OEM Part Supersession History

• 24243901, 24230461, 24241806 → 24252114, 24256960, and others. — Internal revisions and updates by the manufacturer to improve reliability.
  Heads up: These are part numbers for the T42 Transmission Control Module (TCM). While many are physically interchangeable, they MUST be programmed to the vehicle's VIN using GM's Service Programming System (SPS) to function. A used module from another vehicle will not work without reprogramming.