DTC P0117 Engine Coolant Temperature (ECT) Sensor Circuit Low Voltage. Cadillac Concours 1996

For 1990-2009 cars
Engine Controls Components
IAT/ ECT/ TP/ MAP and BBV Sensors
OBD II Symbol Description Notice
ESD Notice
ESD Notice

### Circuit Description

The Engine Coolant Temperature sensor is a thermistor, a sensor whose resistance varies with temperature. The ECT sensor signal is on CKT 410 and sensor ground on CKT 808. As the temperature of the sensor increases, resistance decreases. A high coolant temperature will result in low signal voltage on CKT 410. DTC P0117 sets because the coolant temperature cannot be greater than 147°C (297°F) when the IAT is less than 100°C (212°F) or the vehicle has been driving long enough to cool the engine to less than 147°C (297°F).

### Conditions for Setting the DTC

#### Test Conditions

• | DTCs P0112 and P0113 not set.

• | IAT temperature of 100°C (212°F) or less.

OR

• | DTCs P0122 and P0123 not set.

• | Engine running with throttle angle between 5 and 35 degrees for at least 3.5 minutes.

#### Failure Condition

The ECT sensor reading is 147°C (297°F) or more.

### Action Taken When the DTC Sets

• | PCM turns ON the SERVICE EMISSION SYSTEM message.

• | PCM uses the transaxle temperature sensor values in place of the engine coolant temperature sensor for the first 4.25 minutes of engine operation, and a value of 90°C (194°F) afterwards.

• | Transaxle shift adapts are maintained at current levels.

• | The PCM will illuminate the malfunction indicator lamp (MIL) when the diagnostic runs and fails.

• | The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records.

### Conditions for Clearing the MIL/DTC

• | The PCM will turn the MIL OFF after three consecutive drive trips that the diagnostic runs and does not fail.

• | A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail.

• | A History DTC will clear after forty consecutive warm-up cycles with no failures of any emission related diagnostic test.

• | Use a scan tool to clear DTCs.

• | Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Clearing Diagnostic Trouble Codes in PCM Description and Operation.

### Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

1. With the ECT sensor or wiring shorted, ECT display will read 147°C (247°F) or greater.

2. If ECT display reads -29°C (-20°F) or less with ECT sensor disconnected, wiring is okay but ECT sensor must be shorted.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to A Powertrain On Board Diagnostic (OBD) System Check

2

1. Connect a scan tool.
2. Turn the key ON.
3. View the ECT sensor display.

Is the temperature the same or higher than the value specified?

147°C (247°F)

Go to Step 3

Fault not present.

3 | Disconnect ECT sensor connector. Is the temperature the same or less than the value specified? | -28°C (18°F) | Go to Step 6 | Go to Step 4

4

1. Record the fluid life indexes, turn the key to OFF and wait 30 seconds.
2. Disconnect both PCM connectors.
3. Using DMM J 39200 record and measure the resistance between the ECT sensor signal circuit and a good engine ground.
4. Measure and record the resistance between the ECT sensor signal circuit and the ECT sensor ground circuit.

Is resistance of each measurement greater than the value specified?

10K ohms

Go to Step 8

Go to Step 5

5 | Repair short to ground in th ECT sensor signal circuit or the ECT signal and ground circuits shorted together. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | --

6

1. Check terminal contact at the ECT sensor.
2. Repair terminal contact if needed.

Was terminal contact repaired?

--

Go to Powertrain Control Module Diagnosis for Verify Repair

Go to Step 7

7 | Replace the ECT sensor. Refer to Engine Coolant Temperature (ECT) Sensor Replacement . Is the replacement complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | --

8

1. Check terminal contact at the PCM connector C2 terminal 74.
2. Repair terminal contact if needed.

Was terminal contact repaired?

--

Go to Powertrain Control Module Diagnosis for Verify Repair

Go to Step 9

9 | Replace the PCM. Refer to PCM Replacement/Programming . Is the replacement complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | --