P1437 on 2012-2015 Honda Civic Hybrid: MPI Module Short Circuit Causes and Fixes

What's Unique About the 2012-2015 Honda CIVIC HYBRID

This specific issue is so prevalent on the 2012-2015 Civic Hybrid that American Honda issued Technical Service Bulletin A20-030 on December 18, 2020. The bulletin acknowledges that the Motor Power Inverter (MPI) can fail due to a defective solder joint from the manufacturing process. In response, Honda extended the warranty on this specific part to 15 years or 150,000 miles, whichever comes first. This makes it a well-documented and recognized factory defect rather than a random component failure. The same issue and warranty extension apply to the 2013 Acura ILX Hybrid under TSB 20-021.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Check Engine Light (CEL) illuminated
• IMA (Integrated Motor Assist) warning light on
• Red battery/charging system warning light on
• Brake System warning light on
• Vehicle may not start or may require holding the key for a moment to start
• Vehicle may stall while driving
• Complete loss of hybrid assist, resulting in sluggish, jerky, or rough acceleration
• 12V battery not charging properly, leading to a dead 12V battery
• Power steering warning light on or loss of power steering assist

Most Likely Causes

1. Internal Failure of the Motor Power Inverter (MPI) Module 🔴 High Probability A known manufacturing defect involving a defective solder joint, as documented in Honda TSB A20-030. This defect leads to the burnout of one of the three Insulated Gate Bipolar Transistors (IGBTs) that control the flow of power to the motor, making the unit unrepairable.
   How to confirm: Scan for code P1437 and other related codes listed in TSB A20-030 (such as P1440, P15A5, P0A78). The presence of these codes is the primary confirmation. 🎬 Watch: How to diagnose a failed IMA system step-by-step. A Honda dealer must check the vehicle's VIN against their database (iN VIN status) to confirm eligibility for the warranty extension.
   Typical fix: Replace the Motor Power Inverter (MPI) module. This should be done at a dealership to check for warranty coverage. Honda has released a revised part to address the issue. The repair involves removing the rear seat, powering down the IMA system, and replacing the module within the larger Power Control Unit (PCU) assembly. 🎬 See this walkthrough of the inverter replacement process.
   Est. part cost: $722-$2249

Diagnosis Steps

1. Read the trouble codes with an OBD-II scanner capable of reading hybrid system codes.
2. Confirm if P1437 is present, and check for any other related codes such as P1440, P15A5, P0A78, or P0AE1, which are all listed in the TSB.
3. Immediately reference Honda Service Bulletin A20-030, dated December 18, 2020.
4. Contact a Honda dealership with your Vehicle Identification Number (VIN). Ask them to perform an "iN VIN status inquiry" to check for eligibility under the warranty extension (15 years or 150,000 miles).
5. If the vehicle is eligible, the dealer will perform the repair free of charge according to the TSB.
6. If not eligible (due to mileage, salvage title, or other reasons), the diagnosis is still a failed MPI module that requires replacement. This is a high-voltage component and replacement should only be performed by qualified technicians with the proper safety equipment.

Parts You'll Likely Need

• Motor Power Inverter (MPI) Module / Intelligent Inverter Unit (IIU) Kit (OEM #061B0-RW0-A00) — This is the component that fails internally due to a defective solder joint, as identified by Honda's TSB A20-030. It is sold as a kit and is a revised part designed to prevent future failure.
  Trusted brands: Honda (OEM)
  OEM price range: $722-$900
  Aftermarket price range: Not Available

Related Codes That Often Appear With This One

• P1440 — MPI Module Output Circuit Malfunction. Both codes are listed in TSB A20-030 as resulting from the same internal MPI module failure.
🎬 Watch: A professional diagnosis and repair of the P1440 code.
• P15A5 — Motor Current Sensor Circuit Malfunction. This is another code directly linked to the MPI module's internal failure in TSB A20-030.
• P0A78 — MPI Module Internal Circuit Malfunction. This code also points to the same internal MPI failure described in TSB A20-030.
• P0AE1 — Bypass Contactor Malfunction. This is another related code listed in TSB A20-030 for the same MPI failure.
• P0A27 — High Voltage Contactor Stays Activated. Also listed in TSB A20-030 as a possible concurrent DTC.

Technical Service Bulletins (TSBs) & Recalls

• A20-030: Warranty Extension: 2012-15 Civic Hybrid IMA Motor Power Inverter (MPI) - Published Dec 18, 2020. This TSB is the primary source identifying the cause of P1437 as a defective solder joint in the MPI module and details the extended warranty coverage.
• 20-021: Warranty Extension: 2013 ILX Hybrid IMA Motor Power Inverter (MPI) - Published Dec 18, 2020. This is the equivalent TSB for the Acura ILX Hybrid, which shares the same faulty component.

Platform-Specific Known Issues

• Honda has extended the warranty on the Motor Power Inverter (MPI) to 15 years or 150,000 miles for all 2012-2015 Civic Hybrids due to a high failure rate from a defective solder joint.
• Some owners report being just outside the 150,000-mile limit and facing expensive repairs, with dealer quotes for the job sometimes exceeding $4,000.
• Even if the symptoms and codes perfectly match the TSB, if the vehicle's VIN is not listed as eligible in Honda's system, the warranty claim will be denied.

Mechanic-Grade Diagnostic Values

• Three-Phase Traction Motor Wires Resistance — expected: Not specified, but should be consistent across phases and within manufacturer specs.. Failure: A reading of OL (over-limit) or a significant deviation on one phase indicates a potential short in the motor or wiring that could damage the new MPI module.
• Battery Module Terminal Voltage (After Power-Down) — expected: 30 Volts or less. Failure: If more than 30V is present after following the IMA system power-down procedure, a problem exists in the circuit, and troubleshooting should stop until the high voltage is properly discharged.

Scan Tool Commands That Help

• Honda HDS (or equivalent professional scanner): Inverter Cooling Fan Test — After replacing the MPI module, this function should be used to command the cooling fan to run at various speeds. This verifies that the fan is operational and has proper airflow, which is critical to prevent the new inverter from overheating.
• Honda HDS (or equivalent professional scanner): Calibrations and Resets — After the physical installation of the new MPI module is complete, the technician must use the scan tool to clear all previous fault codes and perform system resets to finalize the repair and ensure the IMA system operates correctly.

Wiring & Ground Locations

• MPI Module / PCU Assembly — Located behind the rear passenger-side seat. The MPI module itself is a component within the larger Power Control Unit (PCU) assembly.. This is the physical location of the failed component. Access requires removing the rear seat and the PCU cover.
• U, V, and W Phase Cables — These three large cables connect the MPI module inside the PCU to the hybrid traction motor at the front of the car.. These cables carry the three-phase AC power to the motor. A pre-installation check for shorts on these cables is recommended to protect the new MPI module. The TSB advises labeling them before disconnection to ensure correct reassembly.
• PCU Ground Cable — A ground cable is attached to the Power Control Unit (PCU) housing.. Like any electronic module, a poor ground can cause a variety of issues. Ensuring this connection is clean and tight during reassembly is critical for proper operation.

Real Owner Repair Stories

• Art's Automotive Blog (2012-2015 Honda Civic Hybrid with 160,000 miles) — IMA warning light on, 12V battery kept going dead, and eventually, the car would not power up at all.
  ❌ Tried (didn't work) A simple component replacement would have missed part of the problem. The car had two separate issues.
  ✅ What actually fixed it The immediate no-power issue was caused by a blown 100A main fuse because the car had been jump-started backward. After bypassing the fuse for testing, the technician found code P0AE1, confirming the separate, common MPI inverter failure. The fix required replacing both the 100A main fuse and the MPI module. The vehicle was over the 150,000-mile warranty limit, so the customer had to pay for the repair.
• Electric Vehicle Forums user (2012 Honda Civic Hybrid with a salvaged title) — IMA light, red battery light, and check engine light came on. Code P1437 was stored.
  ❌ Tried (didn't work) N/A, user was at the beginning of the diagnostic process.
  ✅ What actually fixed it The user was planning to take the car to the dealer but correctly anticipated that the salvaged title would likely void the extended warranty coverage offered by the TSB, even if the failure was identical.
• YouTube repair video (EV & Hybrid Network) (Honda Civic Hybrid (2012-2015 model year)) — IMA system failure with codes P1437, P0A78, P1440.
  ❌ Tried (didn't work) The technician noted that simply replacing the burned-out IGBTs on the board often leads to a repeat failure because of fundamental problems with the control board itself.
  ✅ What actually fixed it The entire MPI module was replaced with a revised OEM part (061B0-RW0-A00) sourced from the USA, as Honda Australia had claimed it was discontinued. Pre-repair checks were done on the motor wiring, and post-repair checks were done on the cooling fan using a scan tool.

OEM Part Supersession History

• 1B200-RW0-000 (Component part number) → 061B0-RW0-A00 (Sold as a kit) — The original MPI module was prone to failure due to a defective solder joint. The replacement kit contains a revised part with visible differences on the circuit board to correct this manufacturing defect.
  Heads up: Attempting to repair the original module by replacing only the failed IGBT transistor is not recommended and often results in a repeat failure due to other issues on the control board.