P2B72 code meaning
Coolant Heater A Control Circuit/Open
What P2B72 means
P2B72 says the command line to coolant heater A is open or has lost continuity. Keep it apart from the engine coolant heater family P01E8–P01EF: the other J2012 codes for this heater – internal module, supply voltage and over-temperature under P2DA4–P2DA7, lost communication under U069E – point to a unit with its own electronics, such as the electric coolant heater of hybrids and EVs. GM's 2013–2014 Volt used a separate coolant heater control module for this job (bulletin PIC5943, no cabin heat in electric mode). No manufacturer documents P2B72 publicly, so limits and timing are unknown. CARB 13 CCR 1968.2 requires circuit monitoring of commanded outputs. In winter the cabin stays cold, or an engine runs more often to supply heat.
P2B72 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P2B72
- Little or no cabin heat, especially in electric driving
- Engine starts more often in cold weather to provide heat (hybrids)
- Warning or fault message, depending on the manufacturer
Common causes of P2B72
- Most likelyCommand wire to the heater broken or connector not latched
- PossibleTerminal pushed back or corroded in the heater connector
- PossibleInput stage of the heater electronics open internally
- Less likelyOutput stage in the commanding control module faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Coolant heater aWiring harnessECM
What each part of P2B72 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| B | Area: hybrid propulsion. |
| 72 | The exact fault in that area. |
What to do next
- Note P2B72 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 P2B72
What does P2B72 mean?
P2B72 means "Coolant Heater A Control Circuit/Open". P2B72 says the command line to coolant heater A is open or has lost continuity. It is a generic code, so it means the same on every make.
Is it safe to drive with P2B72?
P2B72 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will P2B72 fail an emissions test?
P2B72 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is P2B72 to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will P2B72 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.