What causes P1635 on a Honda?

Failed battery condition monitor module inside the IMA pack Corroded BCM connector pins from battery vent gases Open communication line between the BCM and the MCM Deteriorated IMA battery sticks confusing the monitor Blown fuse feeding the BCM circuit

How do I fix P1635 on a Honda?

Read BCM voltage tap data with a Honda HDS scan tool Inspect BCM connectors for corrosion from vent gases Test the BCM-to-MCM communication line for opens Evaluate IMA stick balance since uneven sticks can shadow this code Replace the BCM after confirming wiring and tap voltages

P1635 Battery Condition Monitor Module Malfunction

Q: What does P1635 mean on a Honda?

P1635. Battery Condition Monitor Module Malfunction. Applies to Insight, Civic Hybrid with IMA.

Category: Powertrain - Hybrid Propulsion
Severity: Check Engine Light
Applies to: Insight, Civic Hybrid with IMA

What does P1635 mean on a Honda?

P1635. Battery Condition Monitor Module Malfunction. This Honda-enhanced code applies to Insight, Civic Hybrid with IMA.

Common causes of P1635

Failed battery condition monitor module inside the IMA pack
Corroded BCM connector pins from battery vent gases
Open communication line between the BCM and the MCM
Deteriorated IMA battery sticks confusing the monitor
Blown fuse feeding the BCM circuit

How to fix P1635

Read BCM voltage tap data with a Honda HDS scan tool
Inspect BCM connectors for corrosion from vent gases
Test the BCM-to-MCM communication line for opens
Evaluate IMA stick balance since uneven sticks can shadow this code
Replace the BCM after confirming wiring and tap voltages

Sources and review

Last updated 2026-09-07.