P0603 on 2007-2011 Cadillac DTS: Keep Alive Memory (KAM) Error Causes and Fixes

What's Unique About the 2007-2011 Cadillac DTS

For the Cadillac DTS, this code is often more of an electrical system symptom than a true component failure. A GM Technical Service Bulletin (TSB 05-06-04-060A) acknowledges that P0603 can be set in multiple modules and is often informational, not necessarily indicating a faulty part, frequently triggered by a low voltage condition. This means if you've recently disconnected the battery (located under the rear seat), had a weak battery, or replaced the alternator, seeing this code is a normal consequence and can usually be cleared without further issue after the power supply is stable.

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
• Transmission may shift erratically or harshly
• Rough or unstable idle
• Slight decrease in fuel economy
• Difficulty starting or extended cranking time
• Dimming headlights or flickering interior lights
• Illuminated ABS or traction control light in some cases
• Clicking noise when attempting to start

Most Likely Causes

1. Weak or Failing Battery 🔴 High Probability → Shop Vehicle Battery The DTS has numerous electronic modules that require a stable voltage supply. The battery is located under the rear seat cushion, which can sometimes lead to it being overlooked. An aging battery that can't hold a proper charge, especially during startup, is the most common trigger for this code.
   How to confirm: Use a multimeter to check the battery voltage. It should be ~12.6V with the engine off and 13.7-14.7V with the engine running. Most auto parts stores can perform a free load test to confirm battery health.
   Typical fix: Replace the vehicle's battery. This requires removing the rear seat bottom cushion.
   Est. part cost: $180-$300
2. Loose or Corroded Battery Terminals 🔴 High Probability → Shop Vehicle Battery Battery terminals naturally corrode over time, creating resistance that interrupts the constant power needed by the PCM's memory. Since the battery is under the rear seat, these terminals are often not inspected regularly.
   How to confirm: After removing the rear seat cushion, visually inspect the battery posts and cable ends for white, blue, or green crusty buildup. Check if the cable clamps are tight and cannot be moved by hand.
   Typical fix: Disconnect the battery terminals (negative first), clean them and the battery posts thoroughly with a wire brush, reconnect (positive first), and apply a terminal protector spray.
   Est. part cost: $5-$15
3. Recent Battery Disconnection 🟡 Medium Probability → Shop Vehicle Battery Any service that involves disconnecting the battery (e.g., alternator replacement, battery replacement) will intentionally cut power to the PCM, causing it to lose its Keep Alive Memory.
   How to confirm: If the code appeared immediately after the battery was disconnected for service, this is the cause. A user on CadillacForums.com confirmed P0603 appeared right after an alternator replacement and battery disconnect, which is a common and expected scenario.
   Typical fix: Clear the trouble code with an OBD-II scanner. The code should not return.
   Est. part cost: $0
4. Poor Ground Connections ⚪ Low Probability Corroded or loose main ground straps (from battery to chassis, and chassis to engine block) can cause 🎬 Watch: How to diagnose a bad engine block ground intermittent voltage drops, tricking the PCM into thinking the battery was disconnected.
   How to confirm: Visually inspect the main ground straps for corrosion or damage. Perform a voltage drop test on the ground circuit; it should be less than 0.2 volts.
   Typical fix: Clean the contact points of the ground straps with a wire brush and ensure they are securely fastened.
   Est. part cost: $0-$20

Rare But Worth Checking

• Faulty Negative Battery Cable Assembly: → Shop Vehicle Battery On some GM vehicles of this era, the negative battery cable includes a current sensor that can fail, leading to improper alternator charging and causing a host of electrical issues, including P0603. A user with a 2008 DTS confirmed that replacing this assembly (which contains the faulty sensor) resolved persistent weak starts and dimming lights that a new battery couldn't fix. If your battery and alternator test good but you still have charging system problems, this part is a likely suspect. The ACDelco part number is 22743866.
• Parasitic Electrical Draw: A module or component that fails to 'go to sleep' can drain the battery overnight. This leads to a low voltage state on startup, which triggers the P0603 code. Diagnosis involves using a multimeter to measure amperage draw after the vehicle has been off 🎬 See this step-by-step guide on performing a parasitic draw test for at least 30 minutes. The draw should be less than 50 milliamps.
• Failing Alternator: → Shop Alternator While less common than a bad battery, a failing alternator that produces unstable or low voltage can cause the PCM's memory to reset. With the engine running, the voltage at the battery terminals should be stable, between 13.7 and 14.7 volts. If it is below 13.2V or fluctuates wildly, the alternator is a likely culprit.
• Failing Powertrain Control Module (PCM): → Shop Engine Control Module (ECM) This is the least likely cause. The PCM itself has an internal failure and cannot retain its memory even with a good power supply. This should only be considered after all other power and ground-related possibilities have been exhaustively ruled out.

Diagnosis Steps

1. Check for other DTCs. P0603 is often a symptom of a broader electrical issue.
2. If the battery was recently disconnected for service, clear the code and test drive. If it doesn't return, the issue is resolved.
3. Access the battery under the rear seat cushion. Visually inspect the terminals and cables for corrosion or looseness. Clean and tighten as necessary.
4. Test the battery. Use a multimeter to check for ~12.6V with the engine off. Perform a load test to confirm its health.
5. Test the charging system. With the engine running, check for a stable voltage of 13.7-14.7V at the battery terminals.
6. Inspect main power and ground cables for security and condition.
7. If the code persists with a known-good battery and charging system, test for a parasitic draw. The current should be below 50mA after the car sleeps.
🎬 Watch: Using a scope to find a DTS battery drain
8. If all electrical tests pass, the fault may lie within the PCM, but this is extremely rare.

Parts You'll Likely Need

• Automotive Battery (OEM #ACDelco 94RAGM (or compatible Group Size 94R/H7)) — A weak or failing battery is the number one cause of P0603 on this vehicle.
  Trusted brands: ACDelco, DieHard, Interstate, Duralast
  OEM price range: $220-$300
  Aftermarket price range: $180-$250
• Battery Terminal Cleaner & Protector Kit — Often, the problem is simply a poor connection due to corrosion, which this inexpensive kit can fix.
  Trusted brands: NOCO, CRC
  OEM price range: $10-$20
  Aftermarket price range: $5-$15
• Negative Battery Cable (OEM #ACDelco 22743866) — Can be a rare but notable cause if the integrated current sensor fails, leading to improper charging and various electrical faults.
  Trusted brands: ACDelco, Standard Motor Products
  OEM price range: $40-$60
  Aftermarket price range: $20-$40

Technical Service Bulletins (TSBs) & Recalls

• 05-06-04-060A: An informational bulletin from GM that notes DTCs P0601, P0602, P0603, P0604, etc., can be set in multiple modules. It explicitly warns that a low voltage condition may set these codes and should be repaired before any module is suspected of being faulty.

Platform-Specific Known Issues

• Battery Location and Access: → Shop Vehicle Battery A unique characteristic of the 2007-2011 Cadillac DTS is that the battery is not in the engine bay. It is located under the rear passenger-side seat cushion. To access it, the bottom seat cushion must be removed by pushing it rearward and lifting it up. This location means the battery is often 'out of sight, out of mind,' leading to a lack of regular inspection of the terminals for corrosion.

Mechanic-Grade Diagnostic Values

• Parasitic Draw — expected: < 50-100 milliamps (0.05-0.10 Amps). Failure: A reading significantly higher than 100mA after all modules have gone to sleep (approx. 30-45 minutes).
• Engine Block Ground Cable Voltage Drop — expected: < 0.2 Volts (200 millivolts). Failure: A reading higher than 0.2V indicates high resistance in the ground path between the engine block and the chassis/battery negative.

Scan Tool Commands That Help

• GM Tech2 / High-End Aftermarket: Keep Alive Memory (KAM) Reset — This function is not typically necessary for a P0603 caused by simple power loss. Disconnecting the battery for 30 minutes achieves the same result by allowing capacitors to discharge. It is more appropriately used after replacing a major component that affects adaptive learning, like a throttle body.
• GM Tech2: Crankshaft Position Variation Relearn — This may be required after a complete power loss or PCM reprogramming event. If the engine runs rough or sets a P1336 or P0315 after power is restored, this procedure may be necessary to resynchronize the PCM with the crankshaft position sensor.

Wiring & Ground Locations

• Main Engine Ground Strap — Connects from the engine block (often near the alternator/generator) to the right side body frame rail in the engine compartment.. A corroded, loose, or broken main engine ground is a critical failure point. It can cause intermittent voltage drops to the entire electrical system, tricking the PCM into logging a P0603 code and causing a wide range of other electrical symptoms like dimming lights or a no-crank condition.
• PCM / ECM (Engine Control Module) — Located in the engine bay, under the plastic air intake box assembly on the driver's side. The airbox must be removed to access the module and its connectors.. While rarely the cause, knowing the PCM's location is necessary for advanced diagnosis, such as checking for water intrusion or performing pin-out voltage tests on its power and ground circuits.
• BCM (Body Control Module) — Located on the passenger side, under the dashboard near the right-side kick panel.. While P0603 is primarily a PCM code, severe electrical issues originating from the BCM or its related circuits could potentially contribute to system-wide low voltage conditions.

Real Owner Repair Stories

• ScannerDanner YouTube Channel (Cadillac DTS (year not specified, but same platform)) — No-crank, no-start condition with various electrical anomalies. The starter would not engage.
  ❌ Tried (didn't work) Initial voltage tests at the underhood fuse block showed low voltage, suggesting a bad positive cable or fuse., Testing from the battery positive post to the fuse block also showed a voltage drop.
  ✅ What actually fixed it The main engine block ground strap was completely broken off where it should connect to the block. The engine was not properly grounded to the chassis, causing the starter current to have no return path and creating a floating ground that produced bizarre voltage readings throughout the system. Replacing the broken ground strap resolved the no-start condition.