P1397

Code

Other P — Powertrain

System Voltage Out Of Self Test Range

Brand: Other

Type: P — Powertrain

Views: UK: 37 EN: 100 RU: 54

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Page language: EN

Causes

Weak or discharged battery
Faulty alternator or voltage regulator
Loose or corroded battery terminals or cable connections
Poor engine/chassis ground(s)
Blown fuse or fusible link in the charging/power feed
Damaged or shorted wiring harness or connector to module power supply

Symptoms

Malfunction Indicator Lamp (MIL) or battery warning lamp illuminated
Dim, flickering, or overly bright lighting
Difficult or slow engine cranking
Unexpected engine shutdowns or poor drivability
Erratic instrument cluster or sensor readings
Other electrical accessories not functioning reliably

What to check

Read freeze frame and full DTC list from the vehicle control module
Measure battery resting voltage (key off) and key-on engine-off (KOEO) voltage
Measure charging system voltage with engine running (at idle and higher rpm)
Inspect battery terminals, cable ends, and chassis/engine grounds for tightness and corrosion
Check main power fuses and fusible links
Perform a visual inspection of power wiring and module connectors for damage, corrosion, or water intrusion

Signal parameters

Battery resting voltage (key off) — typical ~12.4–12.8 V when healthy
Key‑on engine‑off (KOEO) bus voltage — typically ~12.4–14.5 V depending on charge state
Charging voltage with engine running — typically ~13.5–14.8 V
Cranking voltage under starter load — typically above ~9–10 V (varies by vehicle)
Voltage ripple on B+ (use oscilloscope) — excessive ripple indicates alternator diode issues
5V sensor reference rails and other module supply voltages (expect stable ~5.0 V and ~12 V where applicable)

Diagnostic algorithm

Retrieve and record freeze frame data and all stored DTCs; note engine speed, load, and exact voltage values at time of fault
Visually inspect battery, terminals, cables, and ground straps; clean and tighten terminals and grounds if corroded or loose
Measure and record battery resting voltage. If below 12.4 V, charge battery fully and load test battery condition
With a charged battery, start engine and measure charging voltage at battery positive to negative at idle and ~2000–3000 rpm; compare to manufacturer spec
Inspect alternator output and measure voltage ripple with an oscilloscope if available to check diode/regulator condition
Check continuity and resistance of main power and ground circuits between battery, alternator, and the affected control module(s)
Inspect and test any fusible links or main power fuses for high resistance or intermittent opening; replace as needed
Wiggle-test wiring and connectors while monitoring voltage to reveal intermittent faults
If voltages remain abnormal after repairs, isolate wiring harness and, if possible, substitute a known-good module or bench-test the control module following manufacturer procedures
After repairs, clear codes and perform a drive cycle or reproduce the self-test condition to verify the DTC does not return

Likely causes

Low battery state of charge or high internal resistance
Alternator output regulating outside spec (over/undercharging)
Corroded/loose battery negative or positive terminal or battery cable
Bad or missing ground strap between engine and chassis/ground point
Intermittent open/short in the B+ feed or sensor 5V reference
Blown main power fuse or fusible link feeding the module

Fault status

⚠️ Status

Control module detected system voltage outside allowed range during self-test. Likely causes include battery, alternator/regulator, wiring/grounds, or a power feed fuse/fusible link issue.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.5 hours

Repair manuals