B1375

Code

OPEL B — Body

Switched System Voltage (Ignition ON) Not Plausible with CAN Signal

Brand: OPEL

Type: B — Body

Views: UK: 3 EN: 9 RU: 5

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Page language: EN

Causes

Low battery or weak battery charge state
Faulty or intermittent ignition-switched power supply (fuse, relay, wiring, connector)
High resistance or missing ground at the affected module
Faulty module reporting incorrect voltage or internal sensor fault
CAN bus corruption, wiring short, open, or poor termination
Intermittent connector corrosion or pin damage

Symptoms

Message stored in module with MIL or body warning lamps illuminated
Intermittent loss or improper operation of body electrical functions (lighting, windows, locks)
Other CAN-related errors or communication faults logged in multiple modules
Vehicle may show battery/charging warning or experience erratic electrical behaviour
Possible no-start or cranking issues if supply is severely low

What to check

Scan vehicle and record all stored DTCs and freeze-frame data from all control modules
Measure battery resting voltage and voltage with ignition ON (key ON, engine OFF) at battery terminals
Measure ignition-switched supply voltage at the affected module power pin with ignition ON
Check main fuses and ignition-switched fuses and relays for continuity and proper operation
Inspect module connectors for corrosion, bent pins, water ingress or loose terminals
Verify module ground(s) for low resistance to chassis (use back-probing and ohmmeter)

Signal parameters

Battery/resting voltage: typically ~12.2–12.8 V (vehicle OFF)
Ignition ON (engine OFF) system voltage: roughly same as battery ~12.2–13.0 V
Charging voltage (engine running): typically ~13.5–14.8 V
CAN bus idle (recessive) voltage: about 2.5 V on CAN_H and CAN_L reference (differential ~0 V)
CAN dominant state: CAN_H ~3.5 V, CAN_L ~1.5 V (differential ~2.0 V)
Expected agreement: module-measured switched voltage should match CAN-reported voltage within ~0.5–1.0 V; larger mismatches trigger plausibility fault

Diagnostic algorithm

Read and document all DTCs and freeze frame data from all modules. Note timestamps and ignition status when code set.
Verify battery condition (state of charge and cranking ability). Charge or replace battery if low.
With a reliable DVOM, measure battery voltage and then measure the switched supply at the affected module with ignition ON. Record values.
Use scan tool to view live CAN-reported system/switched voltage from the module. Compare CAN value to your direct measurement.
Inspect fuses and ignition-switched relays feeding the module. Replace or bench-test suspect relays/fuses.
Inspect and clean the module connectors; back-probe the power and ground pins while wiggling harness to reproduce fault.
Check ground straps and harness grounds for continuity and low resistance to chassis. Repair any high-resistance grounds.
Check CAN physical layer: measure CAN_H and CAN_L idle voltages, check termination resistance (~60 ohms). Use scope to look for noise or interruptions.
If CAN messages show inconsistent or absent voltage data only from one module, address that module (reflash, reprogram, or swap known good if available) after verifying wiring.
After repairs, clear DTCs and perform a road/drive cycle or key cycles to confirm fault does not return. If intermittent, monitor with data logger to capture occurrence.
If all wiring, power, grounds and CAN bus are good and problem persists, consult manufacturer service information for module-specific test procedures or consider module replacement.

Likely causes

Blown/loose ignition-switched fuse or faulty ignition relay supplying the module
High-resistance ground at the module chassis ground strap or engine ground
Corroded connector pin on the module power input or CAN connector
Battery near end of life causing low voltage on ignition ON
Faulty BCM/ECU reporting incorrect CAN voltage value

Fault status

⚠️ Status

Switched system voltage measured locally does not match the voltage value reported on the CAN bus when ignition is ON. Possible causes include supply/ground faults, CAN communication errors, or a failing control module.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours

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B1375 — Switched System Voltage (Ignition ON) Not Plausible with CAN Signal