OBD Code P1605: Loss of KAM Power; Open Circuit

Q: What does OBD code P1605 mean?

Loss of KAM Power; Open Circuit. The engine's computer has lost power to its Keep-Alive Memory (KAM) circuit, which stores important operating data. Think of it like a battery backup for your car's brain suddenly being unplugged.

Q: What are the symptoms of fault code P1605?

Engine starts but runs rough or stalls immediately, Check Engine Light illuminated, Loss of adaptive fuel trim and ignition timing data

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What This Actually Means

In plain language — no jargon

The engine's computer has lost power to its Keep-Alive Memory (KAM) circuit, which stores important operating data. Think of it like a battery backup for your car's brain suddenly being unplugged.

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Symptoms You May Notice

3 known symptoms for this code

Engine starts but runs rough or stalls immediately

Check Engine Light illuminated

Loss of adaptive fuel trim and ignition timing data

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How Your ECU Detects This

Technical sensor logic and voltage thresholds

The ECM monitors continuous 12V power supply to the KAM circuit, which preserves learned values during engine off periods. An open circuit (break in wiring or connector) prevents the ECM from detecting stable voltage on the KAM power line. The fault sets when voltage drops below the minimum threshold required to maintain memory retention.

Voltage & Parameter Thresholds

Parameter	Normal Range	Fault Condition
KAM Circuit Voltage	12V continuous	Below 10.5V or open circuit
KAM Power Supply Continuity	Continuous circuit path	Open or intermittent connection

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Diagnostic & DIY Fix Guide

Check these in order — from cheapest to most complex

1

Battery terminals and connections

Clean corrosion from battery posts and engine ground cables, then reconnect firmly.

2

KAM power fuse (typically 5-10A)

Locate the fuse in the underhood panel and replace if blown or corroded.

3

KAM power supply wiring harness

Inspect for damaged insulation, loose connectors, or pinched wires near the ECM and battery.

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When to See a Professional Mechanic

Not all fault codes are safe to DIY

Code P1605 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.

Safety note: OBD-II codes identify the system or circuit where a fault was detected — they do not always identify the exact failed component. A professional mechanic using live sensor data will diagnose the root cause more accurately than replacing parts based on the code alone.

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How to Clear Code P1605

What happens after you fix the fault

Once the fault is repaired, P1605 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.

The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.

✅ Safe to Clear When

Fault has been diagnosed and repaired
You want to confirm the repair worked
Code appeared after a sensor was cleaned

⚠️ Do Not Clear When

Preparing for an emissions/PUC test
Root cause is still undiagnosed
Check engine light is flashing

Emissions test note: Clearing codes resets OBD readiness monitors. Most vehicles need 50–100 km of mixed driving before monitors complete. Do not clear codes immediately before an emissions or PUC inspection.