P0603 on 2011-2015 Chevrolet Caprice: Keep Alive Memory (KAM) Error Guide

What's Unique About the 2011-2015 Chevrolet CAPRICE

The 2011-2015 Caprice was primarily a Police Patrol Vehicle (PPV) in the U.S. and features a heavy-duty electrical system, often with a dual-battery setup to handle extra equipment. The second (auxiliary) battery in the trunk is managed by an isolation relay. A failing auxiliary battery, faulty isolation relay, or leftover police wiring can cause parasitic drains or voltage instability, making this platform uniquely prone to P0603. Furthermore, General Motors has issued a Technical Service Bulletin (TSB #05-06-04-060A) stating that P0603 is often an informational code that can appear after low voltage events and may not indicate a true component failure.

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.
• No noticeable symptoms other than the light.
• Slightly rough or unstable idle, especially right after starting.
• Hesitation or stumbling during acceleration.
• Harsh or erratic transmission shifting.
• Difficulty starting the engine or intermittent no-start.
• Increased fuel consumption.

Most Likely Causes

1. Weak or Failing Battery (Primary or Auxiliary) 🔴 High Probability → Shop Vehicle Battery The most common reason for a KAM error is an interruption of constant power to the PCM. On a Caprice PPV, this could be the main starting battery or a failing auxiliary battery causing system voltage to drop. Many are purchased from auctions with dead batteries.
   How to confirm: Test the battery with a multimeter (should be above 12.4V with the car off) or have it load-tested at an auto parts store. Check both the primary and auxiliary (if equipped) batteries. A user on capriceppv.com found their auxiliary battery at only 6.5V, causing starting issues.
   Typical fix: Replace the weak or failing battery. If removing the auxiliary battery, ensure the main power feed to it is properly disconnected and insulated to prevent shorts.
   Est. part cost: $150-$350
2. Recent Battery Disconnection or Replacement 🔴 High Probability → Shop Vehicle Battery If the battery was disconnected for any service, the KAM is wiped. This is a normal occurrence and the code is simply logging the event.
   How to confirm: Ask the vehicle owner if the battery has been disconnected or replaced recently. If so, this is the almost certain cause.
   Typical fix: Clear the code with an OBD-II scanner. The code should not return if the electrical system is healthy. The PCM will relearn adaptive values over the next several drive cycles.
   Est. part cost: $0
3. Loose or Corroded Battery Terminals/Grounds 🟡 Medium Probability → Shop Vehicle Battery Corrosion or loose connections at the battery terminals or the main engine/chassis ground straps can cause 🎬 Watch: How to locate ground cables and connections intermittent power loss. A user on the Just Commodores forum reported a persistent P0603 was resolved by finding and replacing a broken negative battery terminal clamp.
   How to confirm: Visually inspect the battery terminals for corrosion. Wiggle the terminal clamps to ensure they are tight. Follow the negative battery cable to the chassis and engine block to check for tightness and corrosion.
   Typical fix: Clean the battery terminals and cable ends with a wire brush. Tighten all connections securely. Replace corroded cable ends or ground straps if necessary.
   Est. part cost: $5-$50
4. Failing Alternator ⚪ Low Probability → Shop Alternator A faulty alternator may not adequately charge the battery, leading to low voltage conditions that can trigger a P0603 code.
   How to confirm: With the engine running, use a multimeter to check the voltage at the battery terminals. A healthy charging system should read between 13.5 and 14.5 volts.
   Typical fix: Replace the alternator.
   Est. part cost: $200-$500

Rare But Worth Checking

• Improperly Installed Aftermarket Electronics: On a former police vehicle like the Caprice, there's a high chance of leftover or poorly removed wiring for lights, sirens, or radios. A GM preliminary information bulletin warns against tapping power from the studs on the isolation relay, as it can cause electrical issues. These can cause parasitic draws or voltage issues, leading to a P0603 code.
• Faulty Auxiliary Battery Isolation Relay: → Shop Vehicle Battery The relay that isolates the auxiliary battery can fail, potentially causing a parasitic drain on the main battery even when the car is off. This can lead to a low voltage condition that triggers P0603 upon startup.
• Faulty Powertrain Control Module (PCM): → Shop Engine Control Module (ECM) This is extremely rare and should only be considered after all other power and ground-related issues have been exhaustively ruled out. A forum member on capriceppv.com ultimately resolved a persistent P0603 by replacing the ECU after confirming all power/ground sources were good, but this is the exception, not the rule.

Diagnosis Steps

1. Check if the code is current or history. If it's a history code from a recent battery change, clear it, drive the vehicle for 15-20 minutes, and see if it returns.
2. Inquire about recent service history. Was the battery recently replaced or disconnected?
3. Test the primary battery's state of charge and health. Use a multimeter for a basic check (12.4V+ engine off) or a load tester for a comprehensive one.
4. If equipped, locate and test the auxiliary battery in the trunk. A dead or failing auxiliary battery is a common problem on these cars and can cause electrical issues.
5. Visually inspect the battery terminals (both batteries), cable ends, and main ground straps for corrosion and tightness. Clean and tighten as needed.
6. With the engine running, test the alternator's output voltage at the battery. It should be approximately 13.5-14.5 volts.
7. Inspect for any non-factory aftermarket wiring, especially around the trunk electrical center. Look for improper taps on the isolation relay studs as warned in GM bulletin PIC5733A.
8. If all power and ground circuits are confirmed to be good and the code persists, the issue may be with the PCM, but this is highly unlikely.

Parts You'll Likely Need

• Car Battery (Primary) (OEM #ACDelco Gold 94RPG (GM Part #88865934)) — A weak or failing primary battery is the number one cause of a P0603 code due to voltage interruption. The BCI Group 94R is a common size for this vehicle.
  Trusted brands: ACDelco, DieHard, Optima
  OEM price range: $200-$350
  Aftermarket price range: $150-$300
• Battery Terminals or Cable Ends — Corroded or damaged terminals prevent a stable power supply to the vehicle's electronics, causing KAM loss. This was the confirmed fix in at least one owner's experience.
  Trusted brands: Dorman, Standard Motor Products
  OEM price range: $20-$50
  Aftermarket price range: $10-$30

Related Codes That Often Appear With This One

• P0601, P0602, P0604, P0606 — These are all internal control module error codes. The provided TSB #05-06-04-060A groups them with P0603, indicating they can be set together during a module-related event, often caused by a low voltage condition.

Technical Service Bulletins (TSBs) & Recalls

• Bulletin #05-06-04-060A: This informational bulletin communicates to technicians that DTCs like P0603 can be shared across multiple modules and are often triggered by low voltage conditions, advising against immediate module replacement.
• Bulletin #PIC5733A: A preliminary bulletin warning about improper electrical connections to the auxiliary battery isolation relay in the trunk of Caprice PPVs, which can cause electrical faults.

Platform-Specific Known Issues

• A GM Technical Service Bulletin (#05-06-04-060A) notes that P0603 is an informational code that can be set across multiple control modules and does not necessarily point to a specific part failure. It often indicates a low voltage event has occurred.
• The dual-battery system in many PPV models adds complexity. A failing auxiliary battery or faulty isolation relay can cause parasitic drains, leading to a low main battery and triggering P0603.
• GM Preliminary Information Bulletin #PIC5733A specifically warns technicians not to use the power studs on the auxiliary battery isolation relay for aftermarket equipment, as it can cause electrical problems.

Mechanic-Grade Diagnostic Values

• PCM Keep Alive Memory (KAM) Power Feed Voltage — expected: Constant Battery Positive Voltage (12.4V+), even with the key off.. Failure: Voltage is 0V or significantly lower than battery voltage, indicating a break in the power supply.
• PCM Ground Circuit Resistance — expected: Less than 1.0 Ohm between the PCM connector ground pins and the chassis ground.. Failure: High resistance (OL or several ohms) indicates a poor ground connection, which can cause floating voltages and module resets.

Scan Tool Commands That Help

• GDS2/Tech2 or equivalent professional scanner: Clear DTCs — This is the primary step after a battery disconnection or replacement. If the code was set simply due to power loss, it will not return after being cleared, provided the electrical system is healthy.
• N/A - Driving Procedure: GM Drive Cycle for Readiness Monitor Reset — After clearing the P0603 code (or any other codes), a specific drive cycle must be performed to allow the PCM to relearn adaptive values and run its self-tests to confirm the repair. This involves a cold start, idling with electrical load, and specific periods of steady-speed driving.

Wiring & Ground Locations

• ECM/PCM Constant Power Fuse — In the rear luggage compartment fuse box (above the battery), fuse F134 (10A) is labeled "ECM BATT" on 2014+ models. For 2011-2013 models, check the rear fuse block (X53A) for a similarly labeled fuse.. This fuse provides the constant battery voltage to the PCM for the Keep Alive Memory. If this fuse is blown or loose, the PCM will lose memory every time the ignition is turned off, setting a P0603.
• X1 Connector — This is one of the main connectors on the Engine Control Module (ECM/PCM) itself, located in the engine bay.. Pin 20 (RD/WH wire) is a primary Battery Positive Voltage feed for the KAM. Probing this pin for constant 12V+ is a key diagnostic step.
• G104 — A primary engine ground point, typically located on the engine block or cylinder head on the passenger's side.. The PCM and many of its sensors rely on a clean ground connection. A loose or corroded G104 can cause intermittent electrical issues, including module resets that trigger P0603.

Real Owner Repair Stories

• capriceppv.com forum user 'smwalker' (2014 Chevrolet Caprice, modified) — P0603 code present, car would not idle correctly after major engine work.
  ❌ Tried (didn't work) Loading different tunes into the ECU., Checking all ground connections., Verifying alternator was charging.
  ✅ What actually fixed it The user identified that fuse F134 (10A) in the trunk fuse box, labeled 'ECM BATT', provides the keep-alive power. While the original poster in that thread ultimately replaced the ECU, the identification of this specific fuse as the direct power source for KAM is a critical diagnostic step that was overlooked.

Model Year Variations Within This Range

• 2011-2013 vs 2014-2015: The entire electrical architecture was updated for the 2014 model year (transition from VE to VF platform). This includes the Body Control Module (BCM), fuse boxes, interior wiring, and the introduction of electric power steering. While the P0603 cause is the same (power loss), the specific fuse numbers (e.g., F134 for ECM BATT on 2014+) and connector locations may differ. An engine harness from a 2011-2013 car will not plug into a 2014+ chassis.
• 2011-2013 vs 2014-2017: The 170-amp alternator has different part numbers between the 2011-2013 and 2014-2017 models, possibly due to differences in how the ECM controls the charging system. While likely interchangeable, using the incorrect year range part could potentially cause subtle charging issues.