GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 1996 🢒 DeVille 🢒 DTC 🢒 DTC P0116 Engine Coolant Temperature (ECT) Sensor Performance

Object Number: 12983 Size: SF
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 circuit uses two pull-up resistors for temperature sensing. When sensor resistance is high indicating low temperatures the PCM uses a 3.65K ohms resistor and a 348 ohms resistor in series. As temperature increases to 50°C (122°F), the sensor resistance will decrease to 973 ohms. This resistance corresponds to 0.97 volt at the PCM. At this point the PCM shifts to the single 348 ohms pull-up resistor to measure temperature above 50°C (122°F). The PCM monitors the voltage signal of the circuit and assumes that engine operation causes coolant temperatures to change at slow rates. This diagnostic test monitors the engine coolant temperature sensor voltage. If the PCM detects a large change in sensor output voltage in a 1 second period, DTC P0116 will set.

Conditions for Setting the DTC

Test Conditions

    • At least 2 seconds have passed since key ON.
    • At least 2 seconds have passed since PCM has commanded a shift in engine coolant temperature pull-up resistors.This occurs when sensor resistance indicates 50°C (122°F).

Failure Condition

Engine coolant temperature sensor voltage has changed 0.3 volts or more in one second.

Action Taken When the DTC Sets

    •  The Malfunction Indicator Lamp (MIL) will not illuminate.
    •  No message will be displayed.

Conditions for Clearing the DTC

    •  A History DTC will clear after forty consecutive warm-up cycles with no failures of any non-emission related diagnostic test.
    •  A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail.
    • 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.

Diagnostic Aids

If fault is not present perform Powertrain Ground Check and also review Failure Rec. to determine conditions under which and how long ago the DTC set.

Test Description

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

  1. Checking DTC P0116 snapshot value to determine if an intermittent high resistance caused the DTC to set.

    2.

  2. An intermittent high resistance can be caused by an open in the ECT sensor signal circuit or the ECT sensor ground circuit.

    3.

  3. An intermittent low resistance can be caused by a short to ground on the ECT sensor signal circuit.

    4.

  4. Checking the ECT sensor's ability to read a full range of temperatures.

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

Are DTCs P0117 or P0118 set?

--

Go to DTCs that are set

Go to Step 3

3

  1. Turn the key ON.
  2. Connect a scan tool.
  3. Select Failure Rec. and note the ECT sensor display.

Is snapshot ECT sensor reading less than the value specified?

-37°C (-35°F)

Go to Step 4

Go to Step 5

4

  1. An intermittent high resistance reading occurred on the ECT sensor circuit.
  2. Look for a possible open on the ECT sensor signal circuit and the ECT sensor ground circuit.
  3. Repair open condition if found.

Was an open condition repaired?

--

Go to Powertrain Control Module Diagnosis for Verify Repair

Go to Step 7

5

Is snapshot ECT sensor reading more then the value specified?

147°C (247°F)

Go to Step 6

Go to Step 7

6

  1. An intermittent low resistance reading occurred on the ECT sensor circuit.
  2. Look for a possible short to ground on the ECT sensor signal circuit.
  3. Repair short if found.

Was a shorted to ground condition repaired?

--

Go to Powertrain Control Module Diagnosis for Verify Repair

Go to Step 7

7

  1. Allow the engine to cool to less than the value specified or artificially cool the engine down.
  2. Start the engine to raise the temperature of the ECT sensor from cool to warm.
  3. As the ECT sensor warms, watch the ECT sensor reading on the scan tool looking for a skip or jump in the value.

Was a skip or jump noted?

35°C (95°F)

Go to Step 8

Fault not present. Refer to Diagnostic Aids

8

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

--