• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
• | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
• | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance |
---|---|---|---|---|---|
ECT Sensor Signal | P0117 | P0118 | P0118 | P0118 | P0116 P0128 |
Low Reference | -- | P0118 | P0118 | P0118 | P0128 |
Circuit | Normal Range | Short to Ground | Open | Short to Voltage |
---|---|---|---|---|
ECT Sensor Signal | -39°C to +120°C (-38°F to +248°F) | 150°C (303°F) | -40°C (-40°F) | -40°C (-40°F) |
Low Reference | -- | -- | -40°C (-40°F) | -40°C (-40°F) |
An ECT sensor monitors the temperature of the coolant. This input is used by the control module for engine control and as an enabling criteria for some diagnostics. The air flow coming into the engine is accumulated and used to determine if the vehicle has been driven within the conditions that would allow the engine coolant to heat up normally to the thermostat regulating temperature. If the coolant temperature does not increase normally or does not reach the regulating temperature of the thermostat, the diagnostics that use ECT as enabling criteria may not run when expected. If the control module detects the calibrated amount of air flow and engine run time have been met, and the ECT has not met the minimum thermostat regulating temperature, DTC P0128 sets.
• | DTCs P0101, P0102, P0103, P0112, P0113, P0117, P0118, P0502, or P0503 are not present. |
• | The startup ECT is less than 75°C (167°F). |
• | The IAT parameter is more than -7°C (+19°F). |
• | The engine run time is between 30-1,800 seconds. |
• | The vehicle is driven more than 0.8 kilometer (0.5 mile) at more than 8 km/h (5 mph). |
• | This diagnostic runs once per ignition cycle when the above conditions are met. |
The control module detects that the actual amount of accumulated air flow is more than the predicted amount of accumulated air flow before the ECT reaches 80°C (176°F).
DTC P0128 is a type B DTCs.
DTC P0128 is a type B DTCs.
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Caution: Under pressure, the temperature of the solution in the radiator can be considerably higher, without boiling. Removing the radiator cap while the engine is hot (pressure is high), will cause the solution to boil instantaneously, with explosive force. The solution will spew out over the engine, fenders, and the person removing the cap. Serious bodily injury may result. Flammable antifreeze, such as alcohol, is not recommended for use at any time. Flammable antifreeze could cause a serious fire.
Important: A critical analysis of the operation of the thermostat is necessary to properly diagnose these DTCs.
Important: All electrical components and accessories must be turned OFF and allowed to power down.
⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM. |
⇒ | If greater than the specified range, test the signal circuit terminal B for a short to ground. If the circuit tests normal, replace the ECM. |
⇒ | If less than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM. |
Measure and record the resistance of the ECT sensor at various ambient temperatures, then compare those measurements to the Temperature vs Resistance table. Refer to Temperature Versus Resistance .
• | Control Module References for PCM replacement, setup, and programming |