Engine Control System & Fuel System - 3.6L - Troubleshooting and Diagnosis: Other GMC Acadia I

Hard Start

1. Test the engine coolant temperature (ECT) sensor. Compare the ECT sensor value to the intake air temperature (IAT) sensor value on a cold engine. The ECT and IAT sensor values should be within ± 3°C (5°F). If the ECT sensor is out of range with the IAT sensor, test the resistance of the ECT sensor. Refer to «Temperature Versus Resistance - Engine Coolant Temperature Sensor»(ref-365318-S26755675792010070600000) for resistance specifications. Replace the ECT sensor if the resistance is not within specification. Refer to «Engine Coolant Temperature Sensor Replacement»(ref-365256-S27411478082010070600000) . If the sensor is within the specification, test the ECT circuits for a high resistance.
2. Test the fuel pump operation. The fuel pump should turn ON for 2 s when the ignition is turned ON. Refer to «Fuel System Diagnosis»(ref-365314-S25281042352010070600000) .

Hesitation, Sag, Stumble

1. Test the fuel pressure. Refer to «Fuel System Diagnosis»(ref-365314-S25281042352010070600000) .
2. Test the generator. Refer to «Symptoms - Engine Electrical»(ref-365260-S34831069102010070600000) . Repair the charging system if the generator output voltage is less than 9 V or more than 16 V.

Poor Fuel Economy

1. Heavy loads being carried or towed
2. Acceleration rate too much or too often
3. Inspect for foreign material accumulation in the throttle bore, and for carbon deposits on the throttle plate and shaft. Also inspect for throttle body tampering.

Poor Fuel Fill Quality

Reference Information

Schematic Reference

Engine Controls Schematics

Electrical Information Reference

1. «Circuit Testing»(ref-365275-S00040570812010070600000)
2. «Connector Repairs»(ref-365275-S19060558252010070600000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-365275-S00287822652010070600000)
4. «Wiring Repairs»(ref-365275-S21384576672010070600000)

Scan Tool Reference

Control Module References for scan tool information

Special Tools

1. CH 48027: Digital Pressure Gage
2. J 26792: Spark Tester

Circuit/System Verification

Note. This diagnostic assumes the following: The battery is completely charged. Refer to Battery Inspection/Test (Acadia or Enclave) or Battery Inspection/Test (OUTLOOK) . The engine cranking speed is acceptable. Refer to Engine Cranks Slowly . There is adequate fuel in the fuel tank.

1. Crank or start the engine. Observe the DTC information with a scan tool. Verify that DTCs P0116, P0118, P0119, P0335, P0336, P0338, P0351-P0356, P0601, P0602, P0604, P0606, P062B, P069E, P0627, P0628, P0629, P167D, P1629, P1631, P1632, P2105 or U0109 does not set. If any of the listed DTCs are set, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(ref-365273-S02566515352010070600000) .
2. Observe the fuel pump control module (FPCM) DTC information with a scan tool. Verify FPCM DTC P0191, P0192, P0193, P0231, P0232, P023F, P025A, P0601-P0604, P0606, P06A6, P062F, P0641, P064A, P1255, P2534, or P2635 is not set. If a DTC is set refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(ref-365273-S02566515352010070600000) .
3. Ignition ON, observe the Theft Deterrent parameter with a scan tool. The parameter should display Disabled. If Enabled is displayed, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(ref-365273-S02566515352010070600000) .
4. Test the ignition system for spark. Refer to «Electronic Ignition System Diagnosis»(ref-365314-S14002203562010070600000) .
5. Ignition ON, command the in-tank fuel pump ON with a scan tool. You should hear the fuel pump turn ON. If the fuel pump does not turn ON, refer to «Fuel System Diagnosis»(ref-365314-S25281042352010070600000) .
6. Ignition ON, observe the FPCM fuel line pressure sensor scan tool parameter. Command an increase in the fuel line pressure with a scan tool. Verify the fuel line pressure increases to greater than 410 kPa (60 psi) as commanded. If less than the specified range, refer to «Fuel System Diagnosis»(ref-365314-S25281042352010070600000) .
7. Verify that the following conditions do not exist: Disconnect the MAF sensor. The engine control module (ECM) will ignore the MAF sensor and default to the calculated air flow. If disconnecting the MAF sensor corrects the condition and the connections are OK, replace the MAF sensor. Refer to «Mass Airflow Sensor with Intake Air Temperature Sensor Replacement»(ref-365256-S30266186522010070600000) .
8. Collapsed air intake duct to the throttle body
9. Restricted air filter element
10. Spark plugs for being gas or coolant fouled - Refer to «Spark Plug Inspection»(ref-365256-S13427409492010070600000) .
11. A skewed engine coolant temperature (ECT) sensor - Refer to «Temperature Versus Resistance - Engine Coolant Temperature Sensor»(ref-365318-S26755675792010070600000) .
12. Exhaust system restricted - Refer to «Restricted Exhaust»(ref-365262-S41652409082010070600000) .
13. Fuel contamination - Refer to «Alcohol/Contaminants-in-Fuel Diagnosis»(ref-365314-S39854230712010070600000) .
14. Engine mechanical condition, for example, worn timing chain and gears, low compression - Refer to «Symptoms - Engine Mechanical»(ref-365315-S40122997512010070600000) .

1. If you find any of the above conditions, repair as necessary.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Fuel System Description

Electrical Information Reference

1. «Circuit Testing»(ref-365275-S00040570812010070600000)
2. «Connector Repairs»(ref-365275-S19060558252010070600000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-365275-S00287822652010070600000)
4. «Wiring Repairs»(ref-365275-S21384576672010070600000)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, command the fuel pump ON and OFF using the scan tool ECM output control. The fuel pump should turn on and off.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for fuel pump control module replacement, setup, and programming

Description and Operation

Fuel System Description

Electrical Information Reference

1. «Circuit Testing»(ref-365275-S00040570812010070600000)
2. «Connector Repairs»(ref-365275-S19060558252010070600000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-365275-S00287822652010070600000)
4. «Wiring Repairs»(ref-365275-S21384576672010070600000)

Scan Tool Reference

Control Module References for scan tool information

Special Tools

1. CH 48027: Digital Pressure Gage
2. CH 48027-100: Digital Pressure Gage
3. J 37287: Fuel Line Shut-Off Adapter

Note. Repair all fuel system related DTCs before performing this diagnostic. Inspect the fuel system for damage or external leaks before proceeding. Verify that adequate fuel is in the fuel tank before proceeding. The fuel pump may need to be commanded ON a few times in order to obtain the highest possible fuel pressure. Before proceeding with this test, review the User Manual CH 48027-5 for Safety Information and Instructions. DO NOT perform the Fuel System Diagnosis if the engine coolant temperature (ECT) is above 60°C (150°F). High fuel pressure readings may result due to hot soak fuel boiling. With the engine OFF, the fuel pressure may increase to the setting of the pressure relief regulator valve, 580 kPa (84 psi).

1. Ignition OFF, all accessories OFF, install a CH 48027: Gage or a CH 48027-100: Gage.
2. Ignition ON, engine OFF, command the fuel pump ON with a scan tool. Verify the fuel pressure is between 345-414 kPa (50-60 psi) and does not decrease greater than 34 kPa (5 psi) in 1 min.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Fuel Feed Pipe Replacement (LLT)»(ref-365256-S22413600502010070600000)
2. «Fuel Line Replacement - Chassis»(ref-365256-S34696899272010070600000)
3. «Fuel Pump Fuel Feed Hose Replacement»(ref-365256-S13522862292010070600000)
4. «Fuel Tank Module Replacement»(ref-365256-S02744259222010070600000)

Schematic Reference

Engine Controls Schematics

Electrical Information Reference

1. «Circuit Testing»(ref-365275-S00040570812010070600000)
2. «Connector Repairs»(ref-365275-S19060558252010070600000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-365275-S00287822652010070600000)
4. «Wiring Repairs»(ref-365275-S21384576672010070600000)

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Fuel Injector Replacement (LLT)

Special Tools

J 44175 Fuel Composition Tester. See Special Tools .

System Verification

The fuel sample should be drawn from the bottom of the tank so that any water present in the tank will be detected. The sample should be bright and clear.

1. If the sample appears cloudy, or contaminated with water, as indicated by a water layer at the bottom of the sample, perform the Particulate Contaminants in Fuel Testing Procedure.
2. If alcohol contamination is suspected, perform the Alcohol in Fuel Testing procedure.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Fuel System Cleaning»(ref-365256-S25240263642010070600000)
2. «Fuel Tank Draining»(ref-365256-S09411239762010070600000)

Vehicle Setup

1. Engine OFF, open the hood. Position a large fan to blow air under the vehicle onto the fuel tank area.
2. Connect the red battery clip from the tester to the positive battery terminal.
3. Connect the black battery clip from the tester to chassis ground.

Smoke Procedure - Locate the Leak

1. Turn OFF any fans that may cause air movement around or near the vehicle.
2. Connect the nitrogen/smoke hose to the vehicle as directed in the service manual. Some vehicles require that the nitrogen/smoke hose be connected at the front of the EVAP system at the EVAP service port. An adapter may be necessary. Other vehicles require the connection be made at the rear of the system using an adapter at the fuel fill cap. Consult the service manual for vehicle specific instructions regarding connection location and adapters.
3. Open the nitrogen tank valve and turn the NITROGEN/SMOKE valve on the control panel to SMOKE.
4. Press and release the remote switch to activate the tester and inject smoke into the EVAP system.
5. Verify smoke has filled the EVAP system by opening the system opposite the end where smoke is injected. When injecting smoke at the service port, remove the fuel fill cap, or temporarily leave the EVAP canister vent valve open, until smoke is observed. Then close the system and continue testing. If using a special tool fuel fill cap adapter at the filler neck, use the J 41413-VLV EVAP Service Port Vent Fitting tool at the service port until smoke is observed, then remove the J 41413-VLV tool and continue with the test. See «Special Tools»(ref-365323-S24558387302010070600000) .
6. Press and release the remote switch to deactivate the tester.
7. Introduce smoke into the system for an additional 60 seconds. Continue introducing smoke at 15-second intervals, as necessary.
8. Using the a high-intensity white light, inspect the entire EVAP system path, and look for the source of the leak indicated by the exiting smoke. Introduce smoke at 15-second intervals, as needed, until leak source is identified.

The Concern

Ideal circumstances for conducting the EVAP Flowmeter Test require equal temperatures between the nitrogen gas and the vehicle EVAP system. Significant differences in temperature between them can result in a flow or pressure change during testing, causing misleading results. Typically, the Evaporative Emissions System Tester is stored indoors, approximately 21°C (70°F). Vehicles brought in for diagnosis may have an EVAP system at significantly different temperatures -40 to +43°C (-40 to +110°F).

For Example

When the EVAP Flowmeter Tests are performed with significant differences in temperature between the nitrogen gas and the vehicle EVAP system, the following results can occur

1. An increase in flow during the flowmeter test can be caused by a vehicle's warm EVAP system cooling down.
2. A decrease in flow during the flowmeter test can be caused by a vehicle's cool EVAP system warming up.

The Solution

When working on a vehicle with significant temperature differences between the vehicle EVAP system and the nitrogen gas, allow the vehicle EVAP system temperature to stabilize as close as possible to the temperature of the nitrogen gas before conducting the Flowmeter Test.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Electronic Ignition System Description

Electrical Information Reference

1. «Circuit Testing»(ref-365275-S00040570812010070600000)
2. «Connector Repairs»(ref-365275-S19060558252010070600000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-365275-S00287822652010070600000)
4. «Wiring Repairs»(ref-365275-S21384576672010070600000)

Scan Tool Reference

Control Module References for scan tool information

Special Tools

1. EL 26792: Spark Tester
2. For equivalent regional tools, refer to «Special Tools»(ref-365323-S24558387302010070600000) .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Ignition Coil Replacement - Bank 1»(ref-365256-S29958321402010070600000)
2. «Ignition Coil Replacement - Bank 2»(ref-365256-S34349929772010070600000)
3. «Control Module References»(ref-365276-S01454229382010070600000) for ECM replacement, setup, and programming

Conditions for Updating the I/M System Status

Each system requires at least one, and sometimes several, diagnostic tests. The results of these tests are reported by a diagnostic trouble code (DTC). A system monitor is complete when either all of the DTCs comprising the monitor have Run and Passed, or any one of the DTCs comprising the monitor have illuminated the malfunction indicator lamp (MIL). Once all of the tests are completed, the I/M System Status display will indicate YES in the Completed column.

For example, when the HO2S Heater Status indicates YES, either all of the oxygen sensor heater tests have passed or one of the tests has illuminated the MIL. If the vehicle has four heated oxygen sensors, either all four heater circuit tests have passed or one of the heater circuit tests has illuminated the MIL. The I/M System Status will indicate NO under the Completed column when any of the required tests for that system have not run. The following is a list of conditions that would set the I/M System Status indicator to NO

1. The vehicle is new from the factory and has not yet been driven through the necessary drive conditions to complete the tests.
2. The battery has been disconnected or discharged below operating voltage.
3. The control module power or ground has been interrupted.
4. The control module has been reprogrammed.
5. The control module DTCs have been cleared as part of a service procedure.

Monitored Emission Control Systems

The OBD II system monitors all emission control systems that are on-board. Not all vehicles need every possible emission control system. For example, a vehicle may not be equipped with secondary air injection (AIR) or exhaust gas recirculation (EGR). The OBD II regulations require monitoring of the following; if equipped

1. The air conditioning system
2. The catalytic converter efficiency
3. Comprehensive component monitoring - Emission related inputs and outputs
4. The evaporative emission (EVAP) system
5. The fuel delivery system
6. Heated catalyst monitoring
7. Misfire monitoring
8. The oxygen sensor system (O2S or HO2S)
9. The oxygen sensor heater system (HO2S heater)

For the specific DTCs required for each system, refer to Inspection/Maintenance System DTC Table . Systems such as misfire and comprehensive components may not be listed in a system status list. These tests run continuously and do not require an I/M System Status indicator.

Review the I/M System Status indicators. All I/M System Status indicators should report YES, and no I/M Test DTCs should be present.

Conditions for Meeting a Cold Start

1. The ignition voltage between 10 and 15 V.
2. The barometric pressure (BARO) is more than 75 kPa.
3. The engine coolant temperature (ECT) at start-up is less than 42°C (108°F).
4. The intake air temperature (IAT) is between 2-32°C (36-90°F).
5. The engine is OFF for greater than 6 hours or the following conditions must be met: The start-up IAT minus start-up ECT are within 12°C (22°F). The start-up ECT minus start-up IAT are within 50°C (90°F).
6. Fuel level is between 25 and 75 %.

Review the Inspection/Maintenance (I/M) System Status indicators. All I/M System Status indicators should report YES, and no I/M Test DTCs should be present.