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Diagnostic Trouble Code (DTC) P1166

Fuel Trim System Lean During Power Enrichment

System Description

The internal circuitry of the Engine control Module (ECM) can identify if the vehicle fuel system is capable of supplying adequate amounts of fuel during heavy acceleration( power enrichment). When a Power Enrichment (PE) mode of operation is requested by heavy acceleration during Closed Loop operation, the ECM will provide more fuel to the engine. Under these conditions the ECM should detect a rich condition. If this reich condition is nor detected at this time, Diagnostic Trouble Code (DTC) P1166 will set. A plugged fuel filter or restricted fuel line can prevent adequate amount of fuel from being supplied during Power Enrichment mode.

Conditions for Setting the DTC

Action Taken When the DTC Sets

Conditions for Clearing the MIL/DTC

Diagnostic Aids

A restricted fuel filter can supply adequate amounts of fuel at idle, but may not be able to supply enough fuel during heavy acceleration.
Water or alcohol fuel may cause low HO2S1 voltage during acceleration.
Check for adequate amount of fuel in the Tank.
When the engine is idling or at steady cruise, the HO2S1 voltage should vary from between approximately a00 to 900 millivolts. During power enrichment mode, more fuel is needed, and the HO2S1 should rise above 444 millivolts.
Check for faulty or plugged injector(s).

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.
  1. The On-Board Diagnostic (EOBD) System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.
  2. This step checks to see if the HO2S1 is operating properly.
  3. If no faults have been found at this point and no additional DTCs were set, refer to "Diagnostic Aids" in this section for additional checks and information.

DTC P1166 - Fuel Trim Supply System Lean During Power Enrichment

Step Action Value(s) Yes No
1
Perform an On-Board Diagnostic (EOBD) System Check.
Is the system check complete?
-
Go to Step 2
Go to "On-Board Diagnostic System Check"
2
  1. Install a scan tool to the Data Link Connector (DLC).
  2. Turn the ignition ON.
Are any component related Diagnostic Trouble Codes (DTCs) set?
-
Go to applicable DTC table
Go to Step 3
3
  1. Check the vehicle for an adequate amount of fuel.
  2. Add fuel to the vehicles fuel tank if the tank is almost empty.
Did the fuel tank require fuel?
-
Go to Step 5
Go to Step 4
4
  1. Using a scan tool, observe the Front Heated Oxygen Sensor (HO2S1) voltage while accelerating the engine over 1200 rpm.
  2. The HO2S1 voltage should vary from specified voltage (100--900 mV) and occasionally toggle above the specified voltage while accelerating.
Is the HO2S1 voltage toggle?
3507 mV
Go to "Fuel System Diagnosis"
Go to "DTC P0134 HO2S Circuit Insufficient Activity Sensor 1"
5
  1. Using the scan tool, clear the Diagnostic Trouble Codes (DTCs).
  2. Start the engine and idle at normal operating temperature.
  3. Operate the vehicle within the conditions for setting this DTC as specified in the supporting text.
Does the scan tool indicate that this diagnostic has run and passed?
-
Go to Step 6
Go to Step 2
6
Check if any additional DTCs are set.
Are any DTCs displayed that have not been diagnosed?
-
Go to Applicable DTC table
System OK

J6B11F25
Display graphicTranslations of text in graphics


Diagnostic Trouble Code (DTC) P1391

Rough Road Sensor Performance

Circuit Description

TThe Gravity Sensing Rough Road (G) sensor is a vertical low g-acceleration sensor. By sensing vertical acceleration caused by bumps or potholes in the road, the Engine Control Module (ECM) can determine if the changes in crankshaft speed are due to engine misfire or are driveline induced. If the G sensor detects a rough road condition, the ECM misfire detection diagnostic will be de-activated. The G sensor at rest output should be between 2.35-2.65 volts (+1G). During a rough road condition, the voltage output can vary between 0.5 (-1G) and 4.5 volts (+3G).

Conditions for Setting the DTC

OR

Action Taken When the DTC Sets

Conditions for Clearing the MIL/DTC

Diagnostic Aids

Check for the following conditions:
Since the G sensor shares the ECM 5 volt reference and ground terminals with the A/C Pressure Sensor, a damaged A/C Pressure Sensor harness or sensor could cause a G sensor DTC to set. Refer to "Multiple ECM Information Sensor DTCs Set" in this section. in this section.
The G sensor will give correct voltages only if it is level and mounted securely to its bracket.
Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the con

Test Description

The number(s) below refer to step(s) on the diagnostic table.
  1. The On-Board Diagnostic (EOBD) System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.

DTC P1391 - Rough Road Sensor Performance

Step Action Value(s) Yes No
1
Perform an On-Board Diagnostic (EOBD) System Check.
Is the system check complete?
-
Go to Step 2
Go to "On-Board Diagnostic System Check"
2
  1. Turn the ignition ON, with engine OFF.
  2. Install a scan tool to the Data Link Connector (DLC).
  3. Review and record the scan tool Failure Records data.
  4. Operate the vehicle within Failure Records conditions as noted.
  5. Using the scan tool, monitor specific Diagnostic Trouble Code (DTC) info for DTC P1391.
Does the scan tool indicate that DTC P1391 failed?
-
Go to Step 4
Go to Step 3
3
Check for the following conditions and repair as needed:
  • G sensor seal missing or damaged.
  • G sensor mounting flanges cracked, missing, or incorrectly installed.
Is the repair complete?
-
Go to Step 14
Go to "Diagnostic Aids"
4
  1. Turn the ignition OFF.
  2. Disconnect the G sensor electrical connector.
  3. Turn the ignition ON, with the engine OFF.
  4. Observe the G sensor value displayed on the scan tool.
Is the G sensor value near the specified value?
0 v
Go to Step 5
Go to Step 12
5
  1. Jumper the 5 volt reference circuit, terminal A and the G sensor signal circuit, terminal B together at the G sensor harness connector.
  2. Observe the G sensor value displayed on the scan tool.
Is the G sensor value near the specified value?
4.95 v
Go to Step 6
Go to Step 7
6
  1. Turn the ignition OFF.
  2. Disconnect the Engine Control Module (ECM) and check the sensor ground circuit for high resistance, an open between the ECM and the G sensor, or for a poor connection at the terminal k34 of the ECM and repair as needed.
  3. f the problem is found, repair as necessary.
Is a problem found?
-
Go to Step 14
Go to Step 10
7
Check the 5 volt reference circuit for high resistance, an open between the ECM and the G sensor, or a poor connection at the terminal k50 of the ECM and repair as needed.
Is the repair complete?
-
Go to Step 14
Go to Step 8
8
  1. Turn the ignition OFF.
  2. Disconnect the ECM and check the G sensor signal circuit for high resistance, an open, a short to ground, or a short to the sensor ground circuit and repair as needed.
Is the repair complete?
-
Go to Step 14
Go to Step 9
9
Check the G sensor signal circuit for a poor connection at the ECM and repair as needed.
Is the repair complete?
-
Go to Step 14
Go to Step 13
10
Check for a poor connection at terminal C of the G sensor and repair as needed.
Is the repair complete?
 -
Go to Step 14
Go to Step 11
11
Replace the G sensor.
Is the repair complete?
-
Go to Step 14
-
12
  1. Turn the ignition OFF.
  2. Disconnect the ECM.
  3. Turn the ignition ON.
  4. Check the G sensor signal circuit for a short to voltage or a short to the 5 volt reference circuit and repair as needed.
Is the repair complete?
-
Go to Step 14
Go to Step 13
13
  1. Turn the ignition OFF.
  2. Replace the ECM.
Is the repair complete?
-
Go to Step 14
-
14
  1. Using the scan tool, clear the DTCs.
  2. Start the engine and idle at normal operating temperature.
  3. Operate the vehicle within the conditions for setting this DTC as specified in the supporting text.
Does the scan tool indicate that this diagnostic ran and passed?
-
Go to Step 15
Go to Step 2
15
Check if any additional DTCs are set.
Are any DTCs displayed that have not been diagnosed?
-
Go to Applicable DTC table
System OK

J6B11F25
Display graphicTranslations of text in graphics


Diagnostic Trouble Code (DTC) P1392

Rough Road Sensor Circuit Low Voltage

Circuit Description

The Gravity Sensing Rough Road (G) sensor is a vertical low g-acceleration sensor. By sensing vertical acceleration caused by bumps or potholes in the road, the Engine Control Module (ECM) can determine if the changes in crankshaft speed are due to engine misfire or are driveline induced. If the G sensor detects a rough road condition, the ECM misfire detection diagnostic will be de-activated. The G sensor at rest output should be between 2.35-2.65 volts (+1G). During a rough road condition, the voltage output can vary between 0.5 (-1G) and 4.5 volts (+3G).

Conditions for Setting the DTC

Action Taken When the DTC Sets

Conditions for Clearing the MIL/DTC

Diagnostic Aids

Check for the following conditions:
Since the G sensor shares the ECM 5 volt reference and ground terminals with the A/C Pressure Sensor, a damaged A/C Pressure Sensor harness or sensor could cause a G sensor DTC to set. Refer to "Multiple ECM Information Sensor DTCs Set" in this section.
The G sensor will give correct voltages only if it is level and mounted securely to its bracket.
Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

Test Description

The number(s) below refer to step(s) on the diagnostic table.
  1. The On-Board Diagnostic (EOBD) System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.

DTC P1392 - Rough Road Sensor Circuit Low Voltage

Step Action Value(s) Yes No
1
Perform an On-Board Diagnostic (EOBD) System Check.
Is the system check complete?
-
Go to Step 2
Go to "On-Board Diagnostic System Check"
2
  1. Turn the ignition OFF.
  2. Install a scan tool to the Data Link Connector (DLC).
  3. Turn the ignition ON, with the engine OFF.
  4. Observe the ROUGH ROAD value displayed on the scan tool.
Is the ROUGH ROAD value near the specified value?
0 v
Go to Step 4
Go to Step 3
3
  1. Review and record the scan tool Failure Records data.
  2. Operate the vehicle within Failure Records conditions as noted.
  3. Using the scan tool, monitor specific Diagnostic Trouble Code (DTC) info for DTC P1392.
Does the scan tool indicate that DTC P1392 failed?
-
Go to Step 4
Go to "Diagnostic Aids"
4
  1. Turn the ignition OFF.
  2. Disconnect the G sensor electrical connector.
  3. Turn the ignition ON, with the engine OFF.
  4. Jumper the 5 volt reference circuit, terminal A and the G sensor signal circuit, terminal B together at the G sensor harness connector.
  5. Observe the G sensor value displayed on the scan tool.
Is the G sensor value near the specified value?
4.95 v
Go to Step 9
Go to Step 5
5
  1. Turn the ignition OFF.
  2. Disconnect the Engine Control Module (ECM) and check the 5 volt reference circuit for an open or short to ground and repair as needed.
Is the repair complete?
-
Go to Step 11
Go to Step 6
6
Check the 5 volt reference circuit for poor connection at the ECM and repair or replace as needed.
Is the repair complete?
-
Go to Step 11
Go to Step 7
7
  1. Turn the ignition OFF.
  2. Disconnect the ECM and check the G sensor signal circuit for an open, a short to ground, or a short to the sensor ground circuit and repair as needed.
Is the repair complete?
-
Go to Step 11
Go to Step 8
8
Check the G sensor signal circuit for a poor connection at the ECM and repair as needed.
Is the repair complete?
-
Go to Step 11
Go to Step 10
9
Replace the G sensor.
Is the repair complete?
-
Go to Step 11
-
10
  1. Turn the ignition OFF.
  2. Replace the ECM.
Is the repair complete?
-
Go to Step 11
-
11
  1. Using the scan tool, clear the DTCs.
  2. Start the engine and idle at normal operating temperature.
  3. Operate the vehicle within the conditions for setting this DTC as specified in the supporting text.
Does the scan tool indicate that this diagnostic ran and passed?
-
Go to Step 12
Go to Step 2
12
Check if any additional DTCs are set.
Are any DTCs displayed that have not been diagnosed?
-
Go to Applicable DTC table
System OK

J6B11F25
Display graphicTranslations of text in graphics


Diagnostic Trouble Code (DTC) P1393

Rough Road Sensor Circuit High Voltage

Circuit Description

The Rough Road (G) sensor is a vertical low g-acceleration sensor. By sensing vertical acceleration caused by bumps or potholes in the road, the Engine Control Module (ECM) can determine if the changes in crankshaft speed are due to engine misfire or are driveline induced. If the G sensor detects a rough road condition, the ECM misfire detection diagnostic will be de-activated. The G sensor at rest output should be between 2.35-2.65 volts (+1G). During a rough road condition, the voltage output can vary between 0.5 (-1G) and 4.5 volts (+3G).

Conditions for Setting the DTC

Action Taken When the DTC Sets

Conditions for Clearing the MIL/DTC

Diagnostic Aids

Check for the following conditions:
Since the G sensor shares the ECM 5 volt reference and ground terminals with the A/C Pressure Sensor, a damaged A/C Pressure Sensor harness or sensor could cause a G sensor DTC to set. Refer to "Multiple ECM Information Sensor DTCs Set" in this section.
The G sensor will give correct voltages only if it is level and mounted securely to its bracket.
Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

Test Description

The number(s) below refer to step(s) on the diagnostic table.
  1. The On-Board Diagnostic (EOBD) System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.

DTC P1393 - Rough Road Sensor Circuit High Voltage

Step Action Value(s) Yes No
1
Perform an On-Board Diagnostic (EOBD) System Check.
Is the system check complete?
-
Go to Step 2
Go to "On-Board Diagnostic System Check"
2
  1. Turn the ignition OFF.
  2. Install a scan tool to the Data Link Connector (DLC).
  3. Start and idle the engine.
  4. Observe the ROUGH ROAD value displayed on the scan tool.
Is the ROUGH ROAD value near the specified value?
4.5 v
Go to Step 4
Go to Step 3
3
  1. Review and record the scan tool Failure Records data.
  2. Operate the vehicle within Failure Records conditions as noted.
  3. Using the scan tool, monitor specific Diagnostic Trouble Code (DTC) info for DTC P1393.
Does the scan tool indicate that DTC P1393 failed?
-
Go to Step 4
Go to "Diagnostic Aids"
4
  1. Turn the ignition OFF.
  2. Disconnect the G sensor electrical connector.
  3. Turn the ignition ON, with the engine OFF.
  4. Note the G sensor voltage displayed on the scan tool.
Is the G sensor value near the specified value?
0 v
Go to Step 5
Go to Step 6
5
Probe the sensor ground circuit terminal C with a test light to B+.
Is the test light ON?
-
Go to Step 7
Go to Step 9
6
Check the G sensor signal circuit for a short to voltage or a short to the 5 volt reference circuit and repair as needed.
Is the repair complete?
-
Go to Step 12
Go to Step 11
7
Check for a poor sensor ground terminal connection at the G sensor electrical connector.
Is the repair complete?
-
Go to Step 12
Go to Step 8
8
Check for a poor sensor ground terminal connection at the Engine Control Module (ECM) and repair as needed.
Is the repair complete?
-
Go to Step 12
Go to Step 10
9
Check the G sensor ground circuit for an open and repair as needed.
Is the repair complete?
-
Go to Step 12
Go to Step 10
10
  1. Turn the ignition OFF.
  2. Replace the ECM.
Is the repair complete?
-
Go to Step 12
-
11
Replace the G sensor.
Is the repair complete?
-
Go to Step 12
Go to Step 10
12
  1. Using the scan tool, clear the DTCs.
  2. Start the engine and idle at normal operating temperature.
  3. Operate the vehicle within the conditions for setting this DTC as specified in the supporting text.
Does the scan tool indicate that this diagnostic ran and passed?
-
Go to Step 13
Go to Step 2
13
Check if any additional DTCs are set.
Are any DTCs displayed that have not been diagnosed?
-
Go to Applicable DTC table
System OK


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