Code
P1197
LINCOLN
P — Powertrain
Key Off Voltage Low
Views:
UK: 13
EN: 21
RU: 26
AI status
Completed
Completed
100%
Causes
- Weak or discharged battery
- Corroded, loose or damaged battery terminals/cables
- Poor chassis or engine ground connections
- Parasitic current draw (modules or aftermarket accessories staying awake or shorted)
- Short to ground in wiring harness or connectors
- Faulty body control module (BCM) or other module reporting voltage incorrectly
Symptoms
- Illuminated MIL or dash warning for electrical/voltage
- Hard starting or no-start after key off period
- Dimmed interior/exterior lights when attempting restart
- Loss of retained accessory power or other unusual electrical behaviors
- Intermittent electrical oddities or modules failing to go to sleep
What to check
- Verify DTC P1197 stored and note freeze frame/store data
- Measure battery voltage at battery posts with key off (vehicle at rest)
- Measure battery voltage at PCM/BCM voltage sense pin(s) and compare to battery posts
- Perform a parasitic current draw test with all modules asleep
- Inspect battery terminals, cable ends and ground straps for corrosion, tightness and physical damage
- Scan for other codes and module communication/awake status
Signal parameters
- Battery voltage at rest (key off) — expected nominal ~12.4 V for a healthy battery; significantly lower values indicate issue
- Voltage at module sense input should closely match battery post voltage
- Parasitic current draw — typical resting draw normally under ~50–100 mA (consult service manual for exact spec)
- Voltage drop across battery cables/ground under load should be minimal (millivolts to low tenths of a volt)
Diagnostic algorithm
- Confirm code and capture freeze-frame data. Note when code set (temperature, voltage).
- With vehicle at rest (all doors closed, keys out), measure battery voltage at posts. If low, try fully charging the battery and re-test.
- Inspect and clean battery terminals and cable ends. Tighten to spec. Re-measure voltages.
- Measure voltage at the voltage-sense pin(s) of BCM/PCM and compare to battery post. Any discrepancy indicates wiring/connection fault between battery and module.
- Perform parasitic draw test: isolate circuits by removing fuses/relays one at a time to find excessive current source. Repair or remove aftermarket loads as found.
- Check all engine/chassis ground straps and main power distribution points for corrosion, looseness or excessive resistance. Repair as needed.
- Wiggle test wiring harnesses in suspect areas while monitoring voltage/current to locate intermittent shorts or opens.
- If wiring and battery are good but low reading persists at module input, test/replace voltage-sensing components or BCM according to factory diagnostics.
- Clear codes and verify the issue does not return under the same conditions. If intermittent, use data logger or extended soak tests to reproduce.
Likely causes
- Battery state of charge low or end of life
- High resistance at battery negative or positive cable or terminal
- Parasitic draw from aftermarket alarm, stereo or lighting
- Loose/poor ground(s) between battery and chassis/engine
- Faulty BCM or voltage sensing input
Fault status
Status
Key Off Voltage Low — controller detected unexpectedly low battery voltage while vehicle is at key-off/rest state.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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