Engine Control System - System & Component Testing: Overview Pontiac Vibe I

Test Description

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

1. 2 This step verifies that the vent port of the solenoid is open.
2. 3 This step verifies that the vent port of the solenoid is now closed.
3. 7 This step tests the control circuit of the solenoid.

The numbers below refer to the step numbers on the diagnostic procedures.

1. 1 The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store the freeze frame data on the scan tool, if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
2. 6 This step will verify the ground path for the EFI relay circuit.

The numbers below refer to the step numbers on the diagnostic procedures.

1. 1 The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store the freeze frame data on the scan tool, if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
2. 2 This step checks for the operation of the fuel pump. Fuel pump operation is difficult to hear without rear seat cushion removal.
3. 5 This step checks for the operation of the circuit opening relay. The circuit opening relay is located in the Instrument Panel Fuse Block and makes an audible click when turning ON and OFF.
4. 7 This step checks the control circuit of the fuel pump relay.
5. 9 The most likely location of an open circuit is between the splice and circuit opening relay terminal No. 2. An inoperative EFI relay would cause no MIL operation. The EFI relay is diagnosed in the No Malfunction Indicator Light diagnostic procedures.
6. 10 This step checks for a fault in the fuel pump or the circuit from the circuit opening relay to the fuel tank. The vehicle should start and run if the only fault was with the circuit opening relay.

System Description

The fuel supply system is a returnless design that has most of the fuel system components located inside of the fuel tank. When the ignition switch is turned to the START position and the engine is cranking, the circuit opening relay will be energized to allow the fuel pump to operate and pressurize the system. The fuel pump will continue to operate if the Powertrain Control Module (PCM) receives a reference signal when the engine is started. The fuel pump operates as long as the circuit opening relay is energized by the PCM. When the circuit opening relay is de-energized, the fuel pump will stop operating. The fuel pump delivers fuel to the fuel rail at high pressure. The fuel pressure regulator, located in the fuel tank, is responsible for keeping the fuel pressure at 44-50 psi (301-347 kPa).

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

1. 1 The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store the freeze frame data on the scan tool, if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
2. 6 This step checks the fuel pump for a worn bearing or a binding impeller. The pump should have a smooth and steady low humming sound. A loud humming or growling noise may indicate a faulty fuel pump. Check a known good vehicle to compare pump operation.
3. 12 The fuel system cannot maintain constant fuel pressure with a leak in any of the following areas: The fuel pump check valve. The valve or valve seat within the fuel pressure regulator. The fuel injectors.
4. 17 This step checks whether the fuel system is leaking between the fuel pressure gauge and the fuel injectors or between the fuel pressure gauge and the fuel sender assembly.
5. 20 This step checks for additional conditions that can cause low fuel pressure other than a faulty fuel pump. Check for any restrictions or blockage in the fuel feed lines and hoses, including those inside the fuel tank. Check the fuel pump electrical circuit for excessive resistance. Proper fuel pump operation requires correct voltage and adequate current flow.
6. 23 Check for rust and other foreign materials in the fuel tank. Clean or replace the fuel tank as necessary.

The numbers below refer to the step numbers on the diagnostic procedures.

1. 1 The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store the freeze frame data on the scan tool, if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
2. 2 This step checks for fuel injector control signals from the PCM.
3. 3 This step checks for a fault that affects all the fuel injectors.
4. 5 This step checks for a short in the fuel injector control circuit.
5. 8 This step checks for ignition positive voltage.

The numbers below refer to the step numbers on the diagnostic procedures.

1. 2 The Engine Coolant Temperature (ECT) affects the ability of the fuel injector tester to detect a faulty fuel injector. Therefore the test results are only valid when the engine coolant temperature is 50-95°F (10-35°C).
2. 3 The first second of the voltage displayed by the DMM may be inaccurate due to the initial current surge, therefore, record the lowest voltage displayed by the DMM after the first second of the test. The voltage displayed by the DMM should be within the specified range. (Scheme 57)for an example. The voltage displayed by the DMM may increase throughout the test as the fuel injector windings warm and the resistance of the fuel injector windings changes. An erratic voltage reading, or large fluctuations in voltage that do not stabilize, indicates an intermittent connection within the fuel injector.

Scheme 57

Scheme 58

1. 2 The engine coolant temperature affects the ability of the fuel injector tester to detect a faulty fuel injector.
2. 3 The first second of the voltage displayed by the DMM may be inaccurate due to the initial current surge, therefore, record the lowest voltage displayed by the DMM after the first second of the test. Voltage displayed by the DMM may increase throughout the test as the fuel injector windings warm and the resistance of the fuel injector windings changes. An erratic voltage reading, or large fluctuations in voltage that do not stabilize, indicates an intermittent connection within the fuel injector. From the voltages recorded, identify the highest voltage, excluding any voltages of more than 9.5 volts. Subtract each voltage that is not more than 9.5 volts from the highest voltage. Record each subtracted value. Refer to the example. (Scheme 59) The subtracted value for any fuel injector must not exceed 0.8 volt. A fuel injector with a subtracted value that is more than 0.6 volt is considered faulty and must be replaced. A fuel injector with a recorded voltage of more than 9.5 volts is also considered faulty and must be replaced.

Scheme 59

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

1. 4 The engine coolant temperature must be below the operating temperature to avoid irregular fuel pressure readings due to hot soak fuel boiling.
2. 5 The fuel pressure should be within the specified range. If the fuel pressure is not within the specified range, refer to Fuel System Diagnosis.
3. 6 The fuel pressure should reach a steady value. If the fuel pressure does not reach a steady value, refer to Fuel System Diagnosis.
4. 7 The fuel injectors are flowing properly if the pressure drop value for each fuel injector is within 10 kPa (1.5 psi) of the average pressure drop value. Calculate the pressure drop value for each fuel injector by subtracting the second pressure reading from the first pressure reading. See «INJECTOR BALANCE TEST EXAMPLE»(ref-152779-S08676921082003031900000) table.

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

1. 1 A Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store the freeze frame data, if applicable. This creates an electronic copy of the data taken when fault occurred. Information is then stored in the scan tool for later reference.
2. 4 This step tests whether PCM can operate the IAC valve using the scan tool commands. IAC valve can be commanded to increase and/or decrease engine speed by using the scan tool RPM CONTROL function. Remember to clear any DTCs and run engine until engine reaches a normal operating temperature before attempting RPM Control using the scan tool.
3. 5 This step checks the operation of both electrical load idle-up circuits. If there is no increase in IAC Motor Command percentage when the electrical accessory is turned ON, idle-up circuit may be inoperative or always ON.
4. 6 This step checks the operation of the A/C idle-up circuit. If there is no increase in the IAC Motor Command percentage when A/C compressor is engaged, idle-up circuit may be inoperative or always ON.
5. 10 This step simulates the Pulse Width Modulated (PWM) signal supplied to the IAC valve by PCM by rapidly grounding and un-grounding terminal No. 1 of the IAC valve.
6. 12 The most likely cause of no ignition positive voltage is an open circuit condition between the IAC valve connector terminal No. 2 and the splice. A shorted or inoperative EFI relay circuit will cause a no-start condition.

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

1. 1 The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
2. 2 This step verifies whether the PCM responds to the operation of the rear defogger. The IAC Motor Command Cycle percentage and the idle speed will increase when the rear defogger is turned ON if the idle-up system is okay.
3. 3 This step verifies whether the PCM responds to the operation of the taillights. The IAC Motor Command Cycle percentage and the idle speed will increase when the taillights are turned ON if the idle-up system is okay.
4. 4 This step verifies the operation of the A/C idle circuit. If the engine idle speed and IAC Motor Command cycle increase when the A/C is turned ON, the A/C idle circuit is functioning normally.
5. 5 This step verifies the operation of the Power Steering Pressure (PSP) switch circuit. If the engine idle speed and IAC Motor Command increase when the steering wheel is turned to 90 percent, the PSP switch idle circuit is functioning normally.
6. 6 This step tests the PSP switch signal circuit for voltage from the PCM.
7. 7 This step tests the operation of the PSP switch.
8. 10 The A/C compressor clutch should not be engaged with the A/C switch Off. The PCM will not increase engine idle speed when the A/C compressor is supposed to be off.
9. 13 If the A/C compressor clutch engages, the compressor clutch, the relay, and the control circuit are all OK. The PCM will then need to be replaced because there was no increase in the IAC motor command percentage during A/C operation in step 4) .
10. 22 This step tests for a short to ground in the diagnostic request circuit. A short to ground in the diagnostic request circuit can cause the PCM to ignore the idle-up signals to the PCM. A short in the diagnostic request circuit will cause the IAC motor command and the idle speed to remain fixed.

Description

Each engine cylinder has a dedicated ignition coil assembly. The ignition coil assembly contains the ignition module circuitry. The power distribution circuit supplies system voltage to each coil assembly when the ignition switch is in the RUN or START positions. Each coil assembly regulates current flow through the primary coil windings, creating a magnetic field. The Powertrain Control Module (PCM) signals each coil assembly to supply a spark in a cylinder through a trigger circuit. Each assembly does so by opening the primary circuit coil, inducing a high voltage in the secondary circuit coil. The high voltage in the secondary circuit grounds by arcing at the spark plug. This event creates a pulse on the fail safe circuit that the PCM recognizes as a confirmation of spark.

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

1. 2 If there is a fault in either the Crankshaft Position (CKP) sensor or Camshaft Position (CMP) sensor circuits, the ignition system can malfunction. Repair the cause of a DTC P0335 or DTC P0340 first.
2. 3 If there is a fault in the electrical circuits between the PCM and the ignition coil assemblies, a DTC P1300-P1315 will set. Use the DTC P1300-P1315 diagnostic procedure to repair the ignition system failure.
3. 7 This step checks for a condition that can cause a loss of spark, even though the test in step 4 indicated that there was good spark.
4. 10 This step checks whether the engine will start and run. A repair that has been performed leading to this step may only have been a contributing cause of a no start condition. Returning to the Engine Cranks but Does Not Run diagnostic procedure will locate additional causes of the no start condition.