P0125

Low engine coolant temperature (ECT) signal inhibiting closed loop fuel control

Detection Conditions

• The ECU monitors the rise in engine coolant temperature after the engine is cold started.  If the engine coolant does not reach a specific temperature within a specified period, the ECU determines that the amount of time for the engine coolant to reach normal operating temperature is too long.  The ECU will continue to operate the engine using open-loop fuel control strategy instead of closed-loop.

Diagnostic Support Notes

• This is a continuous monitor (CCM)
• Check engine indicator illuminates if the ECU detects the above malfunction condition in two consecutive drive cycles
• PENDING CODE is available
• FREEZE FRAME DATA is available
• DTC is stored in ECU memory

Possible Causes

• Engine coolant temperature sensor malfunction
• Thermostat malfunction
• Poor connection or connector between engine coolant temperature sensor and ECU
• Engine cooling fan system malfunction
• Water pump malfunction
• Engine coolant passage restricted and/or coolant leakage
• Engine coolant level/condition
• ECU malfunction

[P0125 - From 1998 and 2002 Mazda Millenia factory service manuals]