Engine Controls - System & Component Testing: Overview Pontiac Aztek I

Test Description

The numbers below refer to step numbers in diagnostic procedure.

1. 3 - Engine Coolant Temperature (ECT) must be below operating temperature in order to avoid irregular fuel pressure readings due to hot soak fuel boiling.
2. 6 - If pressure drop value for each fuel injector is within 1.5 psi (10 kPa) of average pressure drop value, fuel injectors are flowing properly. Calculate pressure drop value for each fuel injector by subtracting second pressure reading from first pressure reading. (Scheme 4)

Scheme 4

The numbers below refer to step numbers in diagnostic procedure.

1. 3 - Engine Coolant Temperature (ECT) must be below operating temperature in order to avoid irregular fuel pressure readings due to hot soak fuel boiling.
2. 4 - Fuel pressure should be within specified range. If fuel pressure is not within specified range, see «FUEL SYSTEM PRESSURE TEST»(ref-152619-S29857367862003021700000) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 3.4L AZTEK & RENDEZVOUS article.
3. 5 - Fuel pressure should reach a steady value. If fuel pressure does not stabilize, see «FUEL SYSTEM PRESSURE TEST»(ref-152619-S29857367862003021700000) under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 3.4L AZTEK & RENDEZVOUS article.
4. 6 - If pressure drop value for each fuel injector is within 1.5 psi (10 kPa) of average pressure drop value, fuel injectors are flowing properly. Calculate pressure drop value for each fuel injector by subtracting second pressure reading from first pressure reading. (Scheme 4)

The numbers below refer to step numbers in diagnostic procedure.

1. 3 - This step tests each fuel injector resistance within a specific temperature range. If any fuel injectors display a resistance outside of specified value, replace fuel injector.
2. 4 - This step determines if all fuel injectors are within 3 ohms of each other. If highest resistance value is within 3 ohms of lowest resistance value, then all fuel injector coil windings are okay.
3. 6 - This step determines if the ignition 1 voltage circuit under the intake plenum is causing the concern.
4. 8 - This step determines which fuel injector is faulty. After subtracting highest and lowest resistance values from average value, replace fuel injector that has greatest resistance difference from average.

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

1. 2 - Command both the ON and OFF states. Repeat the commands as necessary.
2. 3 - This step determines if the condition is located on the coil side or the switch side of the circuit.
3. 4 - This step verifies that the PCM is providing voltage to the fuel pump relay.
4. 5 - This step tests for an open in the fuel pump relay ground circuit.
5. 6 - This step determines if a voltage is constantly being applied to the fuel pump relay.
6. 12 - This tests for a grounded fuel pump supply voltage circuit. The fuel pump fuse supplies power to fuel pump. Disconnecting the fuel pump in-line harness connector isolates the fuel pump supply voltage circuit.
7. 15 - This step jumps the fuel pump relay in order to activate the fuel pump.
8. 16 - This step tests for an open in the fuel pump feed circuit between the in-line connector and the fuel pump relay.
9. 17 - This step tests for an open or high resistance in the fuel pump ground circuit.
10. 20 - This step determines if the condition with the circuit is intermittent. If the fuse does not open, inspect the supply voltage circuit between the fuse and the fuel pump for an intermittent condition.

Description

Fuel Tank Leak Test is used to locate any fuel or fuel vapor escaping fuel tank area. Fuel vapors escaping above fuel level will be detected when Evaporative (EVAP) emission diagnostics complete one test cycle. Malfunction Indicator Light (MIL) will illuminate after EVAP diagnostics complete 2 test cycles.

The numbers below refer to step numbers in diagnostic procedures.

1. 1 - Perform this procedure in order to determine that no EVAP diagnostic DTC is present.
2. 3 - This test is to locate fuel leakage in fuel lines.
3. 4 - This tests for fuel leaks below fuel tank fuel level.
4. 5 - This test is to locate fuel vapors escaping above fuel level in fuel tank.

Engine idle speed is controlled by Idle Air Control (IAC) valve. IAC valve is on throttle body. IAC valve pintle moves in and out of an idle air passage bore to control air flow around throttle plate. IAC valve consists of a movable pintle, driven by a gear attached to a 2 phase bi-polar permanent magnet electric motor called a stepper motor. The stepper motor is capable of highly accurate rotation, or of movement, called steps. The stepper motor has 2 separate windings that are called coils. Each coil is fed by 2 circuits from PCM. When PCM changes polarity of a coil, stepper motor moves one step. PCM uses a predetermined number of counts to determine IAC pintle position. Observe IAC counts with scan tool. IAC counts will increment up or down as PCM attempts to change IAC valve pintle position. An IAC Reset will occur when ignition key is turned OFF. First, PCM will seat IAC pintle in idle air passage bore. Second, PCM will retract pintle a predetermined number of counts to allow for efficient engine start-up. If engine idle speed is out of range for a calibrated period of time, an idle speed DTC may set.

The numbers below refer to step numbers in diagnostic procedure.

1. 5 - This test will determine ability of PCM and IAC valve circuits to control IAC valve.
2. 7 - This test will determine ability of PCM to provide IAC valve circuits with ground. On a normally operating system, test light should not flash while IAC counts are incrementing.