P0C99 code meaning
Hybrid/EV Battery Temperature Sensor L Circuit Low
Powertrain system Generic code P0Cxx codes Check engine light
What P0C99 means
P0C99 reports a sensor L voltage below the valid range. Because the thermistor works against a bias resistor on its monitoring board, any ground fault or an internally shorted sensor drags the voltage down, which reads as a very hot module. GM's 2019 HPC2 table 19OBDG02 flags it once the converted value exceeds 160 °C in 8 out of 10 readings at 100 ms intervals; it is a Type B code and needs supply above 10.2 V. The 2012 Volt table groups L with the other sensors and passes them only at or below 87.5 °C, which equals a raw count of 680 or more, and needs 1.4 s out of 2 s to fail. Mitsubishi does not use L codes. If the pack is really overheating, P0A7E appears instead. Expect a warning lamp and reduced battery power.
P0C99 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor1 to 5 hours
- Clears after repairAfter a drive cycle
Symptoms of P0C99
- Warning lamp and reduced battery power
- Battery cooling running for no apparent reason
Common causes of P0C99
- Most likelySensor L signal shorted to ground
- PossibleThermistor L shorted internally
- Less likelyMonitoring board channel pulling the input low
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Hv battery temp sensor lWiring harnessBms
What each part of P0C99 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| C | Area: hybrid propulsion. |
| 99 | The exact fault in that area. |
What to do next
- Note P0C99 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0C99
What does P0C99 mean?
P0C99 means "Hybrid/EV Battery Temperature Sensor L Circuit Low". P0C99 reports a sensor L voltage below the valid range. It is a generic code, so it means the same on every make.
Is it safe to drive with P0C99?
Drive gently and only to a workshop. With P0C99 the car can go into limp mode (reduced power) to protect itself.
Will P0C99 fail an emissions test?
Yes, it can. P0C99 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0C99 to fix?
Difficulty: workshop only. A typical repair takes 1 to 5 hours of work. This is a job for a workshop.
Will P0C99 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.