EN

Severity: Low Code type: Generic (all makes)

P0603 Code: Internal Control Module Keep Alive Memory (KAM) Error

The engine computer lost its learned memory – usually after a battery disconnect or a bad constant-power feed.

At a glance

Severity: 2/5 – Low2/5

Severity: Low

Meaning
Internal Control Module Keep Alive Memory (KAM) Error
System
ECU & Outputs · Powertrain
Safe to drive?
Yes, short term
Typical repair cost
$0–$1,700
DIY difficulty
Easy

Keep alive memory (KAM) is the part of the ECM that holds learned values while the car is parked: long-term fuel trims, idle airflow, misfire adaptation and, on some vehicles, transmission shift adaptations. It survives only as long as the ECM has an uninterrupted battery feed through its own fuse. If that feed drops out, even for a moment, the ECM finds the stored data missing or implausible at the next start and logs P0603. A battery that was disconnected, ran flat or has a loose clamp is by far the most common trigger, and the code usually stays away once the supply is solid. Only when P0603 keeps returning with a verified good constant feed is the ECM itself suspect.

Can I keep driving? Safe to drive. Expect a slightly unsettled idle or different shift feel for a few trips while the ECM relearns, and fix the power supply so the code doesn't keep coming back.

Try this first – 5-minute fix

  1. Tighten and clean the battery terminals Try to twist each battery clamp by hand – if either moves, clean the post and clamp and tighten it. A clamp that lifts power for a split second over bumps is a classic cause.
  2. Check battery condition Resting voltage should be about 12.4–12.7 V after the car has sat for an hour. Charge a low battery fully and have it load-tested at a parts store.
  3. Clear the code and let the engine relearn Clear P0603, start the engine and let it idle with all accessories off for about 10 minutes, then drive normally. If the code doesn't return within a week, it was the one-time battery event.

How to read P0603

How to read P0603P10263034
  1. P Powertrain
  2. 0 Generic (SAE)
  3. 6 Computer & outputs
  4. 03 Specific fault

Symptoms

  • Check engine light after battery replacement, jump start or a flat battery
  • Idle hunts or stalls when coming to a stop for the first few drives
  • Transmission shifts feel different until it relearns
  • Radio presets and clock reset at the same time
  • Code returns every few days with no battery work done
  • Often no noticeable driveability change at all

Possible causes

Ranked by how often each cause is behind this code (editorial estimate).

  1. Battery was disconnected, replaced or went completely flat (one-off event) 35%
  2. Loose or corroded battery terminal interrupting power intermittently 20%
  3. Weak battery dipping too low during cranking 15%
  4. Blown fuse or bad connection in the ECM's constant-power (KAM) circuit 12%
  5. Internal ECM fault in the keep-alive memory 10%
  6. Parasitic drain deep-discharging the battery overnight 8%

Diagnosis step by step

Diagnostic flow: P06031Link the code to battery work2Inspect terminals and battery cables3Find and test the KAM fuse4Measure the constant feed at the ECM5Check for parasitic drain if thebattery goes flat6Condemn the ECM last

  1. Link the code to battery work

    Ask whether the battery was replaced, disconnected, jump-started or ran down. On many vehicles a single P0603 after such an event is expected and needs nothing more than a clear.

    Tools: OBD-II scanner

  2. Inspect terminals and battery cables

    Check both clamps for tightness, white or green corrosion under the clamp and a cracked cable end. Follow the negative cable to its body and engine grounds as well.

    Tools: Flashlight, Soft brush

  3. Find and test the KAM fuse

    Locate the ECM's constant-power fuse in the underhood box (often labeled PCM, ECM or keep alive). Check both sides with a test light or meter with the key off – battery voltage should be present on both.

    Tools: Multimeter

  4. Measure the constant feed at the ECM

    Back-probe the ECM's constant-power pin with the key off; it should read within about 0.2 V of battery voltage. Wiggle the harness and fuse box while watching for dropouts.

    Tools: Multimeter

  5. Check for parasitic drain if the battery goes flat

    With the car locked and modules asleep, current draw is usually below about 50 mA. A higher draw that empties the battery overnight will erase KAM again and again.

    Tools: Multimeter

  6. Condemn the ECM last

    If P0603 returns while the constant feed is verified solid and the battery is healthy, the memory inside the ECM is faulty. That's uncommon and requires a programmed replacement.

    Tools: OBD-II scanner

Where the parts are

Charging system and control modules – P06031234567
Charging system and control modules
  1. 1Battery
  2. 2Alternator
  3. 3Engine computer (ECM)
  4. 4CAN bus
  5. 5Transmission
  6. 6Wheel speed sensor
  7. 7High-voltage battery

Repair options & costs

RepairDIY?Estimated cost
Clean and tighten battery terminals Yes $0–$30
Replace weak battery Yes $150–$350
Repair KAM fuse holder or constant-power wire No $60–$200
Locate and fix a parasitic drain No $100–$350
Replace ECM with programming No $700–$1,700

Rough US estimates for parts and labor; shop rates vary by region. Not a quote.

Notes by brand

Ford

On many Ford vehicles, P0603 is logged after the battery has been disconnected or has run flat, because the PCM's keep-alive memory has been erased. One occurrence after battery work is normal; if it returns without any, check the battery clamps and the PCM keep-alive power fuse before suspecting the PCM.

Field data

Nissan 2 Pathfinder, Rogue

Source: NHTSA Complaints API (US government open data), analyzed by DTC mention.

Emissions / smog test impact

Depends

Whether P0603 lights the check engine light depends on the vehicle; if the light is on, the car fails the OBD test. Clearing the code or disconnecting the battery also resets the readiness monitors, so drive a few days before testing.

Frequently asked questions

Why did P0603 show up right after I installed a new battery?

Removing the battery cut the ECM's constant power, so its learned values were wiped. The ECM notices the empty memory at the next start and records P0603. Clear it once; it shouldn't come back.

Will the car drive differently after a KAM reset?

Briefly, yes. Idle may hunt, the engine may stall once at a stop, and an automatic can shift a little firmly until it relearns over several drives.

How do I help the ECM relearn idle?

Start the engine with everything off, let it idle about 10 minutes until the cooling fan cycles, then drive normally with some stop-and-go. Some vehicles have a specific idle relearn in the scan tool, which is quicker.

Does a memory saver prevent P0603 during a battery swap?

Usually, because it keeps the ECM's constant feed alive through the OBD port. Be careful: the memory saver also powers live battery cables, so keep the disconnected clamp from touching the body.

Sources