Description

This DTC is set when the Engine Coolant Temperature (ECT) does not reach 75°C (167°F) despite sufficient engine warm-up time having elapsed.

DTC No.

DTC Detection Conditions

Trouble Areas

P0128

Conditions (a), (b) and (c) met for 5 seconds (2 trip detection logic):

(a) Cold start

(b) Engine warmed up

(c) ECT less than 75°C (167°F)

• Thermostat

• Cooling system

• ECM

MONITOR DESCRIPTION

The ECM estimates the ECT based on the starting temperature, engine loads, and engine speeds. The ECM then compares the estimated temperature with the actual ECT. When the estimated ECT reaches 75°C (167°F), the ECM checks the actual ECT. If the actual ECT is less than 75°C (167°F), the ECM interprets this as a malfunction in the thermostat or the engine cooling system and sets the DTC.

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