Aston Martin diagnostic trouble code

P0128: Coolant Thermostat (Coolant Temp Below Regulating Temperature)

Use this reference to understand the recorded condition, confirm the available V8 Vantage or DB9 manual coverage, and follow the documented diagnostic checks before replacing parts.

Code family
Powertrain
Vehicle system
Cooling and temperature
Manual coverage
V8 Vantage, DB9
Warning-lamp status
V8 Vantage: MIL; DB9: MIL

What Aston Martin code P0128 means

Coolant Thermostat (Coolant Temp Below Regulating Temperature)

DB9 preliminary diagnostic manual · section 2-32

Manufacturer fault-analysis procedure

Manual fault definition

P0128 - The coolant temperature is below the
thermostat regulating temperature.

Cautions and notes

CAUTION: This code should be generated only in
the primary PCM.
This code is generated if the engine coolant does
not reach operating temperature level within x
minutes of engine start.

Test sequence and decision path

1. Connect the WDS or scan tool and confirm that
P0128 is present.

2. Clear the P0128 code and run a KOER test to
check that P0128 is not logged again.

3. If P0128 is logged again, check for other coolant
temperature sensor codes (P0116, 0117 or 0118).
If present, resolve these codes first and return to
step 4 of this procedure if P0128 is logged again
after clearing the P0116, 0117 or 0118 code.

4. If P0128 is logged again, fit a new coolant thermostat. Clear the P0128 code and run a KOER
test until the engine is fully warmed up to check
that the problem is resolved.
Open the corresponding manual page for wiring diagrams and figures