P1290, P1292, P1293

DTC Code	DTC Name
P1290	Engine Coolant Temperature Circuit
P1292	Short in Engine Coolant Temperature Circuit
P1293	Open in Engine Coolant Temperature Circuit

DESCRIPTION

A thermistor is built into the Engine Coolant Temperature (Radiator) sensor, of which the resistance value varies according to the Engine Coolant Temperature (Radiator).

The structure of the sensor and its connection to the ECM are the same as those of the Intake Air Temperature (IAT) sensor.

Tech Tips

When any of DTCs P1290, P1292 and P1293 are set, the ECM enters fail-safe mode. During fail-safe mode, the ECT is estimated to be 80°C (176°F) by the ECM. Fail-safe mode continues until a pass condition is detected.

DTC No.	Proceed To	DTC Detection Conditions	Trouble Areas
P1290	Step 1	Open or short in Engine Coolant Temperature (Radiator) sensor circuit for 0.5 seconds (1 trip detection logic)	Open or short in Engine Coolant Temperature (Radiator) sensor circuit Engine Coolant Temperature (Radiator) sensor ECM
P1292	Step 4	Short in Engine Coolant Temperature (Radiator) sensor circuit for 0.5 seconds (1 trip detection logic)	Short in Engine Coolant Temperature (Radiator) sensor circuit Engine Coolant Temperature (Radiator) sensor ECM
P1293	Step 2	Open in Engine Coolant Temperature (Radiator) sensor circuit for 0.5 seconds (1 trip detection logic)	Open in Engine Coolant Temperature (Radiator) sensor circuit Engine Coolant Temperature (Radiator) sensor ECM

DTC No.

Proceed To

DTC Detection Conditions

Trouble Areas

P1290

Step 1

Open or short in Engine Coolant Temperature (Radiator) sensor circuit for 0.5 seconds

(1 trip detection logic)

Open or short in Engine Coolant Temperature (Radiator) sensor circuit
Engine Coolant Temperature (Radiator) sensor
ECM

P1292

Step 4

Short in Engine Coolant Temperature (Radiator) sensor circuit for 0.5 seconds

(1 trip detection logic)

Short in Engine Coolant Temperature (Radiator) sensor circuit
Engine Coolant Temperature (Radiator) sensor
ECM

P1293

Step 2

Open in Engine Coolant Temperature (Radiator) sensor circuit for 0.5 seconds

(1 trip detection logic)

Open in Engine Coolant Temperature (Radiator) sensor circuit
Engine Coolant Temperature (Radiator) sensor
ECM

Tech Tips

When any of these DTCs are set, check the Engine Coolant Temperature (Radiator) by selecting the following menu items on an intelligent tester: Powertrain / Engine and ECT / Data List / Coolant Temp 2.

Temperature Displayed	Malfunctions
-40°C (-40°F)	Open circuit
140°C (284°F) or higher	Short circuit

MONITOR DESCRIPTION

The Engine Coolant Temperature (Radiator) sensor is used to monitor the Engine Coolant Temperature (Radiator). The Engine Coolant Temperature (Radiator) sensor has a thermistor with a resistance that varies according to the temperature of the engine coolant. When the coolant temperature is low, the resistance in the thermistor increases. When the temperature is high, the resistance drops. These variations in resistance are reflected in the voltage output from the sensor. The ECM monitors the sensor voltage and uses this value to calculate the Engine Coolant Temperature (Radiator). When the sensor output voltage deviates from the normal operating range, the ECM interprets this as a fault in the Engine Coolant Temperature (Radiator) sensor and sets a DTC.

Example:

If the sensor voltage output is -40°C (-40°F) for 0.5 seconds or more, the ECM determines that there is an open in the Engine Coolant Temperature (Radiator) sensor circuit, and sets DTC P1293. Conversely, if the voltage output is more than 140°C (284°F) for 0.5 seconds or more, the ECM determines that there is a short in the sensor circuit, and sets DTC P1292.

If the malfunction is not repaired successfully, a DTC is set 0.5 seconds after the engine is next started.

WIRING DIAGRAM

INSPECTION PROCEDURE

Tech Tips

If other DTCs relating to different systems that have terminal E2 as the ground terminal are output simultaneously, terminal E2 may have an open circuit.
Read freeze frame data using an intelligent tester. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can be helpful in determining whether the vehicle was running or stopped, whether the engine was warmed up or not, whether the air-fuel ratio was lean or rich, as well as other data recorded at the time of a malfunction.

PROCEDURE

READ VALUE USING INTELLIGENT TESTER (RADIATOR COOLANT TEMPERATURE)

Connect an intelligent tester to the DLC3.
Turn the ignition switch to the ON position.
Turn the tester ON.
Select the following menu items: Powertrain / Engine and ECT / Data List / Coolant Temp 2.

Read the value displayed on the tester.

Standard
Between 80°C and 97°C (176°F and 207°F) with warm engine.

Result

Temperature Displayed	Proceed To
-40°C (-40°F)	A
140°C (284°F) or higher	B
Between 80°C and 97°C (176°F and 207°F)	C

Tech Tips

If there is an open circuit, the intelligent tester indicates -40°C (-40°F).
If there is a short circuit, the intelligent tester indicates 140°C (284°F) or higher.

B

READ VALUE USING INTELLIGENT TESTER (CHECK FOR SHORT IN HARNESS) Click here

C

CHECK FOR INTERMITTENT PROBLEMS

A

READ VALUE USING INTELLIGENT TESTER (CHECK FOR OPEN HARNESS)
1. Confirm good connection of the connector to the ECM (Radiator).
2. Disconnect the B29 Engine Coolant Temperature (Radiator) sensor connector.
3. Connect terminals 1 and 2 of the Engine Coolant Temperature (Radiator) sensor connector on the wire harness side.
4. Connect the intelligent tester to the DLC3.
5. Turn the ignition switch to the ON position.
6. Turn the tester ON.
7. Select the following menu items: Powertrain / Engine and ECT / Data List / Coolant Temp 2.
8. Read the value displayed on the tester.
  
  Standard
  
  140°C (284°F) or higher
9. Reconnect the Engine Coolant Temperature (Radiator) sensor connector.
OK
REPLACE ENGINE COOLANT TEMPERATURE SENSOR

NG
READ VALUE USING INTELLIGENT TESTER (CHECK FOR OPEN IN ECM)
1. Confirm good connection of the connectors to the ECM.
2. Disconnect the B29 Engine Coolant Temperature (Radiator) sensor connector.
3. Connect terminals THW and E2 of the ECM connector.
  
  Tech Tips
  
  Before checking, perform visual and contact pressure checks on the ECM connector.
4. Connect the intelligent tester to the DLC3.
5. Turn the ignition switch to the ON position.
6. Turn the tester ON.
7. Select the following menu items: Powertrain / Engine and ECT / Data List / Coolant Temp 2.
8. Read the value displayed on the tester.
  
  Standard
  
  140°C (284°F) or higher
9. Reconnect the Engine Coolant Temperature (Radiator) sensor connector.
OK
REPAIR OR REPLACE HARNESS OR CONNECTOR

NG

REPLACE ECM
READ VALUE USING INTELLIGENT TESTER (CHECK FOR SHORT IN HARNESS)
1. Disconnect the B29 Engine Coolant Temperature (Radiator) sensor connector.
2. Connect the intelligent tester to the DLC3.
3. Turn the ignition switch to the ON position.
4. Turn the tester ON.
5. Select the following menu items: Powertrain / Engine and ECT / Data List / Coolant Temp 2.
6. Read the value displayed on the tester.
  
  Standard
  
  -40°C (-40°F)
7. Reconnect the Engine Coolant Temperature (Radiator) sensor connector.
OK
REPLACE ENGINE COOLANT TEMPERATURE SENSOR

NG
READ VALUE USING INTELLIGENT TESTER (CHECK FOR SHORT IN ECM)
1. Disconnect the D1 ECM connector.
2. Connect the intelligent tester to the DLC3.
3. Turn the ignition switch to the ON position.
4. Turn the tester ON.
5. Select the following menu items: Powertrain / Engine and ECT / Data List / Coolant Temp 2.
6. Read the value displayed on the tester.
  
  Standard
  
  -40°C (-40°F)
7. Reconnect the Engine Coolant Temperature (Radiator) sensor connector.
OK
REPAIR OR REPLACE HARNESS OR CONNECTOR

NG

REPLACE ECM

SFI SYSTEM (w/ Secondary Air Injection System), Diagnostic DTC:P1290, P1292, P1293