DTC 1-2-3
1-2-3 ENGINE COOLANT TEMPERATURE SENSOR SIGNALPreconditions for DTCs
^ If the ECM receives a signal from the Engine Coolant Temperature (ECT) sensor which indicates a temperature lower than -45°C (-49°F) (high signal) or higher than +15O°C (3OO°F) (low signal) this is interpreted as a fault and DTC 1-2-3 is set.
Substitute values
^ At start-up, a substitute value of +2O°C (68°F) is assumed, rising after start-up to +83°C (181°F).
^ The engine cooling fan starts running at half speed.
^ The IAC valve's idle air trim is inhibited.
^ Long term fuel trim inhibited.
Fault sources
^ Signal too high:
- Signal lead short circuited to voltage.
- Break in signal or ground lead.
- Contact resistance in connectors.
- Defective ECT sensor.
^ Signal too low:
- Signal lead short circuited to ground.
- Defective ECT sensor.
^ Incorrect signal:
- Defective ECT sensor.
- Defective coolant thermostat.
- Contact resistance in connectors.
- Signal lead short circuited to another lead.
Fault symptoms
^ Difficulty in starting in certain temperature ranges.
^ Engine fan runs for 3 minutes after engine shutdown.
TESTING PROCEDURE
Other DTCs
^ Check for other DTCs.
If DTC 3-1-4, 4-1-1 and possibly 4-1-3 are stored:
- Check the joint coupling at pin A18 on the ECM for signs of contact resistance and oxidation and for breaks.
If none of the above DTCs are stored:
- Check Status message.
Status Message
^ Check current status message.
If Status message is: Permanent fault, signal too high:
- Proceed to: PERMANENT FAULT, SIGNAL TOO HIGH section below.
If Status message is: Permanent fault, signal too low:
- Proceed to: PERMANENT FAULT, SIGNAL TOO LOW section below.
If Status message is: Permanent fault, faulty signal:
- Proceed to: PERMANENT FAULT, FAULTY SIGNAL section below.
If Status message is: Intermittent fault, signal too high:
- Proceed to: INTERMITTENT FAULT, SIGNAL TOO HIGH section below.
If Status message is: Intermittent fault, signal too low:
- Proceed to: INTERMITTENT FAULT, SIGNAL TOO LOW section below.
If Status message is: Intermittent fault, faulty signal:
- Proceed to: INTERMITTENT FAULT, FAULTY SIGNAL section below.
CAUTION: Engine cooling fan can run at half speed.
PERMANENT FAULT, SIGNAL TOO HIGH
CAUTION: Before beginning the fault tracing process, the Engine Cooling Fan (FC) relay connector A must be disconnected to prevent the fan from working. DTC 5-1-4 Engine cooling fan half speed, signal can be set.
After fault tracing, the connector MUST WITHOUT FAIL be re-connected.
Checking the Ground Lead
^ Switch Ignition OFF.
^ Wait for about 150 seconds.
^ Disconnect the ECT sensor.
^ Connect an ohmmeter between the ECT sensor's connector 2 (to ECM) and ground.
NOTE: Any fan run-on must be allowed to finish before resistance measurements are carried out.
The ohmmeter shows approx. 0 ohms.
If reading is OK:
- Check the signal lead.
If reading is incorrect:
- Check the ECM's connector.
Checking the Signal Lead
^ Switch Ignition ON.
^ ECT sensor disconnected.
^ Connect a voltmeter between the ECT sensor's connectors 1 and 2 (to the ECM).
The voltmeter should show approx. 5 Volts.
If reading is OK:
- Check the ECT sensor's resistance.
If the voltmeter shows approx. 0 Volts:
- Check the ECM's connector.
If the voltmeter shows more than approx. 5 Volts:
- Check the lead between the ECT sensor's connector 1 and ECM A31 for signs of short circuiting to voltage.
- After rectification: Check the ECT sensor.
Checking the ECM's Connector
^ Switch Ignition OFF.
^ ECT sensor disconnected.
^ Remedy the ECM's connector with regard to contact resistance and oxidation.
^ ECM connected.
^ Connect an ohmmeter between ECT sensor connector 2 (to control module) and ground.
The ohmmeter should show approx. 0 ohms.
If reading is OK:
- The source of the DTC is poor contact in the ECM's connector.
If reading is incorrect:
- Check the lead between the ECT sensor's connector 2 and ECM A18 for signs of a break.
Checking the ECT Sensor's Resistance
^ Switch Ignition OFF.
^ ECT sensor disconnected.
^ Connect an ohmmeter between ECT sensor connectors 1 and 2 (to ECT sensor).
The ohmmeter should show approx. 2200 ohms at +25°C (77°F).
If reading is OK:
- The source of the DTC is poor contact in the ECT sensor's connector. Rectify the connector with regard to contact resistance and oxidation.
It reading is incorrect:
- Test with a new ECT sensor.
Checking the ECT Sensor
^ The ECT sensor can break as a sequential fault resulting from short circuiting of the signal lead to voltage supply. Check the ECT sensor as follows.
^ Switch Ignition OFF.
^ ECT sensor disconnected.
^ Connect an ohmmeter between ECT sensor connectors 1 and 2 (to ECT sensor).
The ohmmeter should show approx. 2200 ohms at +25°C (77°F).
If reading is OK:
- ECT sensor is OK.
If reading is incorrect:
- Test with a new ECT sensor.
Checking the ECM's Connector
^ Switch Ignition OFF.
^ ECT sensor disconnected.
^ Rectify the ECM's connectors with regard to contact resistance and oxidation.
^ ECM connected.
^ Switch Ignition ON.
^ Connect a voltmeter between ECT sensor connectors 1 and 2 (to ECM).
The voltmeter should show approx. 5 Volts.
If reading is OK:
- The source of the DTC is poor contact in the ECM's connector.
If reading is incorrect:
- Check the lead between the ECT sensor connector 1 and ECM A31 for signs of a break.
PERMANENT FAULT, SIGNAL TOO LOW
CAUTION: Before the fault tracing process is begun, the Engine Cooling Fan (FC) relay connector A must be disconnected to prevent the fan from operating. DTC 5-1-4 Engine cooling fan half speed, signal can be set.
After fault tracing, the connector MUST WITHOUT FAIL be re-connected.
Checking the Signal Lead
^ Switch Ignition OFF.
^ Disconnect the ECT sensor.
^ Switch Ignition ON.
^ Connect a voltmeter between ECT sensor connector 1 (to ECM) and ground.
The voltmeter should show approx. 5 Volts.
If reading is OK:
- Test with a new ECT sensor.
If reading is incorrect:
- Check the lead between the ECT sensor's 1 and ECM A31 for signs of short circuiting to ground.
PERMANENT FAULT, FAULTY SIGNAL
CAUTION: Before the fault tracing process begins, the Engine Cooling Fan (FC) relay connector A must be disconnected, to prevent the fan from operating. DTC 5-1-4 Engine cooling fan half speed, signal can be set.
After fault tracing, the connector MUST WITHOUT FAIL be re-connected.
Checking the ECT Signal
^ Switch Ignition ON.
^ Connect multimeter P/N 9996525 to temperature box P/N 9995281 and temperature sensor P/N 9995282.
^ Carefully remove the expansion tank lid.
WARNING: RISK OF SCALDING WATER.
^ Undo the hose between the engine's rear edge and the radiator pack.
^ Insert the sensor into the hose.
^ Refit the hose and expansion tank lid.
^ Look up pre-defined list 09.
^ START the engine and let it run at idling speed.
^ Check that the Volvo System Tester shows the correct temperature. There may be a difference of a couple of degrees owing to the difference in temperature sensor location.
If the Volvo System Tester shows the correct engine coolant temperature:
- Test with a new coolant thermostat.
If the Volvo System Tester shows the wrong engine coolant temperature:
- Check the ECT sensor.
Checking the ECT Sensor
^ Switch Ignition ON.
^ Look up the DTC parameter.
^ Disconnect the temperature sensor.
^ Read off the voltage at the ECT sensor.
Voltage should be approx. 5 Volts.
If reading is OK:
- Check the lead.
If the reading deviates:
- Check the control module's connector.
Checking the Control Module's Connector
^ Switch Ignition OFF.
^ ECT sensor disconnected.
^ Rectify the control module's connector with regard to contact resistance and oxidation.
^ Control module connected.
^ Switch Ignition ON.
^ Look up the DTC parameter.
^ Read off the voltage at the ECT sensor.
Voltage should be approx. 5 Volts.
If reading is OK:
- The DTC was caused by poor connection in the control module's connector.
If the reading deviates:
- Check the lead between the ECT sensor connector 1 and control module A31 for signs of short circuiting to another lead.
Checking the Ground Lead
^ Switch Ignition OFF.
^ Wait for about 150 seconds.
^ ECT sensor disconnected.
^ Connect an ohmmeter between ECT connector 2 (to control module) and ground.
The ohmmeter should show approx. 0 ohms.
If reading is OK:
- Test with another ECT sensor.
If reading differs:
- Check the control module's connector.
Checking the Control Module's Connector
^ Switch Ignition OFF.
^ ECT disconnected.
^ Rectify the control module's connector with regard to contact resistance and oxidation.
^ Control module connected.
^ Connect an ohmmeter between ECT connector 2 (to control module) and ground.
The ohmmeter should show approx. 0 ohms.
If the reading is OK:
- The DTC was caused by poor contact in the control module's connector.
If the reading differs:
- Check the lead between the ECT connector 2 and control module A18 for signs of a break.
INTERMITTENT FAULT, SIGNAL TOO HIGH
CAUTION: Before the fault tracing process begins, the Engine Cooling Fan (FC) relay connector A must be disconnected, to prevent the fan from operating. DTC 5-1-4 Engine cooling fan half speed, signal can be set.
After fault tracing, the connector MUST WITHOUT FAIL be re-connected.
Checking the Leads And Connections
^ Check the ECT sensor's and ECM's connectors for loose connections and contact resistance and oxidation.
^ Check the lead between the ECT sensor connector 1 and ECM A31 for signs of an intermillent break and intermittent short circuiting to voltage supply.
^ Check the lead between the ECT sensor connector 2 and ECM A18 for signs of an intermittent break.
INTERMITTENT FAULT, SIGNAL TOO LOW
CAUTION: Before the fault tracing process begins, the Engine Cooling Fan (FC) relay connector A must be disconnected, to prevent the fan from operating. DTC 5-1-4 Engine cooling fan half speed, signal can be set.
After fault tracing, the connector MUST WITHOUT FAIL be re-connected.
Checking the Leads And Connections
^ Check the lead between the ECT sensor's connector 1 and ECM A31 for signs of intermittent short circuiting to ground.
INTERMITTENT FAULT, FAULTY SIGNAL
CAUTION: Before the fault tracing process begins, the Engine Cooling Fan (FC) relay connector A must be disconnected, to prevent the fan from operating. DTC 5-1-4 Engine cooling fan half speed, signal can be set.
After fault tracing, the connector MUST WITHOUT FAIL be re-connected.
Checking Leads And Connections
^ Check the ECT sensor's and control module's connectors for signs of a loose connection and for contact resistance and oxidation.
^ Check the lead between the ECT sensor connector 1 and control module A31 for signs of short circuiting to another lead.
^ If no fault can be found: Test with a new ECT sensor.