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Home >> Cadillac >> 2006 >> STS Base, 3.6 7, AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - 3.6L - DTC P0008 To P0128 >> DTC P0118 >> Test Description
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Test Description

The numbers below refer to the step numbers in the diagnostic table.

  1. 6:  This step is testing the low reference circuit for a short to voltage or for a low reference circuit that is open. If the low reference circuit within the ECM is open or if the low reference circuit is open between the ECM and the splice, a voltage of 3-5 volts will be measured on the DMM.
  2. 7:  This step isolates if there is a circuit that is shorted to voltage or if the low reference circuit is open internally or externally of the ECM. If there is no voltage on the low reference circuit after disconnecting all the sensors, the low reference circuit is open.
DTC P0118

Step Action Values Yes No
Schematic Reference:  Engine Controls Schematics 
Connector End View Reference:  Engine Control Module Connector End Views  or  Engine Controls Connector End Views 
1 Did you perform the Diagnostic System Check - Vehicle? - Go to Step 2  Go to Diagnostic System Check - Vehicle
2
  1. Turn ON the ignition, with the engine OFF.
  2. Observe the ECT sensor parameter with a scan tool.
Is the temperature less than the specified value?		 -39°C (-38°F) Go to Step 4  Go to Step 3 
3
  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition?		 - Go to Step 4  Go to Diagnostic Aids
4
  1. Turn OFF the ignition.
  2. Disconnect the engine coolant temperature (ECT) sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage from the signal circuit of the ECT sensor to the engine control module (ECM) housing with a DMM.
Is the voltage within the specified range?		 4.8-5.2 V Go to Step 5  Go to Step 8 
5
  1. Turn OFF the ignition.
  2. Remove the ECM/TCM fuse from the underhood electrical center.
    3. NOTE: Do NOT use a test lamp to test the continuity of the circuit. Damage to the control module may occur due to excessive current draw.
  3. Measure the resistance between the low reference circuit of the ECT sensor and the ECM housing with a DMM.
Is the resistance less than the specified value?		 5 ohm Go to Step 12  Go to Step 6 
6 
  1. Install the ECM/TCM fuse into the underhood electrical center.
  2. Turn ON the ignition, with the engine OFF.
  3. Measure the voltage between the low reference circuit of the ECT sensor and the ECM housing with a DMM. Refer to Circuit Testing .
Is the voltage more than the specified value?		 1.0 V Go to Step 7  Go to Step 14 
7 
  1. Turn OFF the ignition.
  2. Disconnect all components that share the low reference circuit.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage between the low reference circuit of the ECT sensor and the ECM housing with a DMM. Refer to Circuit Testing .
Is the voltage more than the specified value?		 1.0 V Go to Step 15  Go to Step 11 
8 Is the voltage more than the specified value? 6 V Go to Step 9  Go to Step 10 
9
IMPORTANT: The ECT sensor may be damaged if the circuit is shorted to battery positive voltage.
Test the signal circuit between the ECT sensor and the ECM for a short to voltage. Refer to Circuit Testing and Wiring Repairs .Did you find and correct the condition?		 - Go to Step 18  Go to Step 13 
10 Test the signal circuit between the ECT sensor and the ECM for an open or for high resistance. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 18  Go to Step 13 
11 Test the low reference circuit between the ECT sensor and the ECM for an open or for high resistance. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 18  Go to Step 13 
12 Test for an intermittent and for a poor connection at the ECT sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .
Did you find and correct the condition?		 - Go to Step 18  Go to Step 16 
13 Test for an intermittent and for a poor connection at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .
Did you find and correct the condition?		 - Go to Step 18  Go to Step 17 
14 Repair the open in the low reference circuit of the ECT sensor between the splice and the ECT sensor. Refer to Wiring Repairs .
Did you complete the repair?		 - Go to Step 18  -
15
IMPORTANT: The control module and/or the ECT sensor may be damaged if the circuit is shorted to battery positive voltage.
Repair the short to voltage in the low reference circuit of the ECT sensor. Refer to Wiring Repairs .Did you complete the repair?		 - Go to Step 18  -
16 Replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement .
Did you complete the replacement?		 - Go to Step 18  -
17 Replace the ECM. Refer to Control Module References for replacement, setup, and programming.
Did you complete the replacement?		 - Go to Step 18  -
18
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition?		 - Go to Step 2  Go to Step 19 
19 Observe the Capture Info with a scan tool.
Are there any DTCs that have not been diagnosed?		 - Go to Diagnostic Trouble Code (DTC) List - Vehicle System OK
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