P0126moderate severityPowertrain
Insufficient Coolant Temperature for Stable Operation
on 2023 Chevrolet Bolt EUV 65 kWh Single Motor FWD · FWD
What this code means
The engine is not reaching or holding a stable operating temperature. This is often caused by a thermostat stuck open.
Symptoms
- Poor heater output
- Poor fuel economy
- Longer warm-up time
Common causes
- Thermostat stuck open
- Faulty engine coolant temperature sensor
- Low coolant level
- Faulty cooling fan running constantly
Diagnostic steps
- Monitor coolant temperature at warm-up
- Inspect thermostat operation
- Test coolant temperature sensor
- Replace thermostat or sensor as needed
🔌 Don't have a code reader?
Any of these will read and clear this code — pick by how deep you want to go.
Budget handheld~$40
ANCEL AD410 →
No-phone-needed handheld — reads, clears, live data, freeze frame.
✓ ANCEL official store
Serious DIY~$100
BlueDriver Pro →
Enhanced codes (ABS, airbag, TPMS) plus repair reports.
SHOP FAVORITEShop-grade tablet~$300
Autel MaxiCOM MK808S →
Bidirectional tests, service resets, all systems.
✓ Autel official store
Pro diagnostics$1,500+
Autel MaxiSys MS906 Pro →
Full-system pro platform — topology mapping, ECU coding, the works.
✓ Autel official store
As an Amazon Associate and Autel/ANCEL partner, OLP earns from qualifying purchases — how we link. This never changes the specs we publish.
Other Powertrain codes on this vehicle
P0005
Fuel Shutoff Valve A Control Circuit/Open
P0006
Fuel Shutoff Valve A Control Circuit Low
P0007
Fuel Shutoff Valve A Control Circuit High
P0008
Engine Position System Performance - Bank 1
P0009
Engine Position System Performance - Bank 2
P0026
Intake Valve Control Solenoid Circuit Range/Performance Bank 1
P0027
Exhaust Valve Control Solenoid Circuit Range/Performance Bank 1
P0028
Intake Valve Control Solenoid Circuit Range/Performance Bank 2
P0029
Exhaust Valve Control Solenoid Circuit Range/Performance Bank 2
P0033
Turbocharger/Supercharger Bypass Valve Control Circuit