The P0B77: Hybrid Battery Voltage Sense “M” Circuit code indicates an issue with the voltage sensing circuit for hybrid battery “M.” This could be due to a faulty voltage sensor, wiring problems, or a malfunction in the control module. If unresolved, this can result in improper voltage monitoring, affecting the performance and efficiency of the hybrid system.
P0B77 – Quick Overview
| Code | Information |
|---|---|
| Meaning | P0B77: Hybrid Battery Voltage Sense “M” Circuit |
| Is it serious? | Yes, improper voltage monitoring can affect hybrid battery performance and system reliability. |
| Possible causes | – Faulty voltage sensor M – Wiring issue – Control module fault |
| How to diagnose? | – Test voltage sense M circuit – Inspect wiring and connections – Check control module functionality |
P0B77 Meaning
The P0B77 code is triggered when the voltage sense “M” circuit in the hybrid battery detects a malfunction. This could be caused by a faulty sensor, wiring problems, or a control module issue. If left unresolved, improper voltage readings may lead to inaccurate battery monitoring, impacting hybrid system performance.
Step-by-step diagnostic guide
| Action | Description | Tools Needed |
|---|---|---|
| Check for Other Codes | Use an OBD-II scanner to check for additional related codes that may give more context to the issue. | OBD-II Scanner |
| Test Voltage Sense M Circuit | Use a multimeter or diagnostic tool to measure the voltage in the sense M circuit and compare it to manufacturer specifications. | Multimeter, Diagnostic Tool |
| Inspect Wiring and Connections | Inspect the wiring and connectors for any signs of damage, corrosion, or loose connections that could affect the voltage sense M circuit. | Flashlight, Multimeter, Safety Gloves |
| Check Control Module Functionality | Use a diagnostic tool to test the control module and ensure it is properly communicating with the voltage sense M circuit. Replace or reprogram the module if necessary. | Diagnostic Tool |
| Clear the Code and Test Drive | After completing repairs, clear the code and take the vehicle for a test drive to ensure the issue is resolved. | OBD-II Scanner, Vehicle Owner’s Manual |
| Recheck for Codes | Rescan the vehicle after the test drive to confirm that the P0B77 code does not return. | OBD-II Scanner |
Free PDF: How to choose OBD2 scanner
I’ve made you a free PDF to choose the OBD2 scanner in 5 minutes.
✅ Which OBD2 scanner is best?
✅ Which type should you get (DIY, Pro, Hobby)
✅ What is the best scanner for the exact brand/feature (e.g best for BMW)
✅ How to get a Bi-Directional tool for as cheap as $40
✅ Discount coupons for scanners
PDF is 100% free and it is designed to help you pick a scanner in less than a few minutes! Not a boring 50-page guide.
Just tell me where to send it.
Hi, I am Juraj “Yuri” Lukacko. I got frustrated by unhelpful and scammy mechanics, so I decided to learn everything about car diagnostics myself. I test dozens of new car diagnostic tools every month along with learning new strategies to fix and customize cars. About Juraj Lukacko (Yuri)