P1634: Motor Power Inverter (MPI) Module Signal Circuit Malfunction (Honda)
Severity: medium
What it means: On Honda hybrids like the 2010–2014 Insight, P1634 means the hybrid control computer has a problem with the signal circuit to the motor power inverter (the module that powers the IMA motor). Owners often see it together with P1448 when a fan or fuse problem knocks out power to that part of the IMA system.
Safe to drive? Usually OK for short drives, but the IMA system may shut down and the 12V battery may stop charging. Get it checked soon.
Common symptoms
- IMA warning light
- Battery or check engine light
- No electric assist
Likely causes, ranked
- Blown IMA fuse that also powers the fan circuitDIY
- Wiring or connector problem in the IMA systemShop
- Inverter module faultShop
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Vehicle-specific notes
- 2010–2014 Honda Insight: On InsightCentral, an owner with about 225,000 km had P1634 and P1448 together, and members blamed a failed IMA fan. Read the full answer · Source
DIY or shop?
DIY for checking fuses. Further diagnosis needs a shop with Honda's scan tool.
Before you replace parts
- Read all IMA codes.
- Check the IMA fuses.
- Fix any P1448 (fan) problem first, then clear codes and recheck.
- Have a Honda-savvy shop test the inverter circuit if it returns.
Safety / mechanic note
Verify with a mechanic. If the 12V battery stops charging, the car can stall. A code points to a circuit or system, not always a specific part.
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