Circuit Description
The ECU monitors the ECT sensor while the engine is warming in order to determine how long the engine takes to achieve a specified coolant temperature increase required for a Closed Loop operation.
A DTC sets if the ECU determines that the engine does not achieve a predetermined engine temperature increase in a specified amount of time. This DTC will not run if either the intake air or the engine coolant temperature measures below a specific temperature. The ECU will only run this DTC on a cold start and only once per cold start.
This is a type A DTC.
Conditions for Setting the DTC
The following conditions will set the DTC:
| • | The vehicle is in the CNG operation mode. |
| • | The engine run time is greater than 500 seconds. |
| • | None of the following DTCs are active: 14, 15, 23, 25. |
| • | The intake air temperature is greater than -15°C (5°F). |
| • | The vehicle speed is greater than 5 mph. |
| • | The minimum calculated airflow is GREATER than 8.5 gps. |
| • | The ECT at start is less than 33°C (91°F). |
| • | The ECT is greater than -17°C (1°F). |
Action Taken When the DTC Sets
The ECU will set DTC 16 and illuminate the MIL lamp after 1 fault has occurred.
Conditions for Clearing the MIL/DTC
The ECU turns the MIL OFF after 3 consecutive driving trips without a fault condition present. A DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 40°C (72°F) from the start-up coolant temperature and the engine coolant temperature exceeds 70°C (160°F) during that same ignition cycle) or the code clearing procedure has been used.
Diagnostic Aids
A skewed ECT sensor or a stuck open thermostat will cause a DTC 16 to set.
An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation.
| • | Check for a poor connection or a damaged PCM harness. Inspect the ECT sensor signal circuit and the ground circuit terminals for the following conditions: |
| - | Improper mating |
| - | Broken locks |
| - | Improperly formed connectors |
| - | A poor terminal to wire connection |
| - | Damaged harness |
| • | Perform an intermittent test. If the connections and the harness check OK, monitor a digital voltmeter connected between ECT sensor signal circuit and ground circuit terminals while moving the related connectors and the wiring harness. If a fault is induced, the resistance reading will change. This may help in order to isolate the location of the malfunction. |
| • | Use the Temperature vs. Resistance table in order to evaluate the possibility of a skewed sensor. Refer to Temperature vs. Resistance in Engine Controls -- 2.2L in the J Platform Service Manual. |
Test Description
The number(s) below refer(s) to the step number(s) on the Diagnostic Table.
-
Allow the engine to fully cool. The ECT sensor and the IAT sensor will read close to the ambient temperature in order to check for a possible skewed ECT sensor.
-
Measure the engine coolant temperature with a thermometer in order to determine what the actual value the ECT sensor should be. Take into consideration if the engine has been operating and if the engine coolant has been warmed without opening the thermostat.
-
This step simulates a DTC 14. The ECU and wiring are OK if the ECU stores a DTC after two ignition cycles.
-
The ECT sensor, the ECU and the wiring have checked OK at this point. Check for a proper thermostat and a proper cooling fan operation.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Alternative Fuels (AF) Powertrain On-Board (OBD) System Check performed? | -- | Go to Step 2 | Go to AF Powertrain OBD System Check |
If the coolant temperature is close to operating temperature, follow this procedure:
If the coolant temperature is close to ambient air temperature, follow this procedure:
Are the readings close? | -- | Go to Step 4 | Go to Step 3 | |
Does the ECT sensor accurately reflect the actual engine coolant temperature? | -- | Go to Step 4 | Go to Step 8 | |
4 | Disconnect the ECT sensor electrical connector. Is the ECT sensor value less than the specified value? | -30°C (-22°F) | Go to Step 5 | Go to Diagnostic Aids |
Was DTC 14 present? | -- | Go to Step 6 | Go to Step 7 | |
Check for a proper cooling system operation and repair any problems as necessary. Was a repair necessary? | -- | Go to Step 9 | Go to Diagnostic Aids | |
7 |
Was a repair necessary? | -- | Go to Step 9 | Go to Diagnostic Aids |
8 | Replace the ECT sensor. Is the action complete? | -- | Go to Step 9 | -- |
9 |
Does this diagnostic run and pass? | -- | Go to Step 10 | Go to Step 2 |
10 | Are any ECU or PCM DTC's displayed that have not been diagnosed? | -- | Go to applicable DTC table | System OK |
