Engine Controls - Basic Diagnostic Procedures: Overview Pontiac Aztek I

Test Description

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

1. 3 - This step determines if ignition relay is providing listed fuses with voltage.
2. 5 - This step determines if the fuel pump is operating electrically.
3. 6 - If all the Cylinder Injector Circuit Status parameters display FAULT, this indicates a condition with the injector supply voltage circuit.

1. Perform diagnostic system check. See «DIAGNOSTIC SYSTEM CHECK -- ENGINE CONTROLS»(ref-155075-S24848794192003060600000) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 3.4L AZTEK & RENDEZVOUS article. After performing diagnostic system check, go to next step.
2. Turn ignition on, with engine off. Using scan tool, check for DTCs. If DTCs P0101, P0230, P0336, P0601, P0602, P1626, P1630 or P1631 are set, diagnose DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-155075-S27919636112003060600000) in SELF-DIAGNOSTICS - 3.4L AZTEK & RENDEZVOUS article. If DTC(s) are not set, go to next step.
3. Using a test light, probe both sides of the following fuses: ELEC, ENG and Fuel INJ fuses. Does test light illuminate on at least one side of the fuses listed? If yes, go to next step. If no, diagnose or replace ignition relay.
4. Turn ignition off. Disconnect a spark plug wire. Install a Spark Tester (J 26792) to spark plug wire. Attempt to start engine. Is spark present at spark tester? If yes, go to next step. If no, diagnose electronic ignition system. See «IGNITION SYSTEMS»(ref-152619-S40142985842003021700000) .
5. Using scan tool, command fuel pump ON. Does the fuel pump turn on? If yes, go to next step. If no, diagnose fuel pump electrical circuit. See «FUEL SYSTEMS»(ref-152619-S32565021802003021700000) .
6. While monitoring the cylinder 1-6 injector circuit status parameters with scan tool, crank engine. Do all of the Cylinder Injector Circuit Status parameters display OK while cranking the engine? If yes, go to next step. If no, diagnose fuel injector. See «FUEL INJECTOR COIL TEST»(ref-153136-S02728456852003031900000) under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 3.4L AZTEK & RENDEZVOUS article.
7. Turn ignition off. Reinstall all disconnected components. Install Fuel Pressure Gauge (J 34730-1A). Turn ignition on, with engine off. Using scan tool, command fuel pump on. Is fuel pressure within 52-59 psi (358-405 kPa)? If yes, go to next step. If no, perform fuel system diagnosis. See «FUEL SYSTEMS»(ref-152619-S32565021802003021700000) .
8. Check for collapsed air intake duct, restricted air filter element, fouled spark plugs, engine mechanical condition or restricted exhaust system. Check ECT sensor value (ECT sensor is NOT close to actual engine temperature), compare MAP/BARO parameters to another vehicle (parameters should be close in value) or check TP sensor for being stuck in range. Did you find and correct the condition? If yes, go to next step. If no, problem is intermittent.
9. Using scan tool, clear any DTCs that are set. Attempt to start engine. Does engine start and continue to operate? If yes, go to next step. If engine does not start, go to step 2 .
10. Allow engine to reach operating temperature. Observe DTC information on scan tool. Does the scan tool display any DTCs that you have not diagnosed? If yes, diagnose affected DTC. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-155075-S27919636112003060600000) in SELF-DIAGNOSTICS - 3.4L AZTEK & RENDEZVOUS article. If no, system is okay.

System Description

PCM turns on the in-tank fuel pump when ignition is on. The fuel pump will remain on as long as engine is cranking or running and PCM is receiving ignition reference pulses. If there are no ignition reference pulses, PCM will turn the fuel pump off 2 seconds after ignition is turned on or 2 seconds after engine stops running. The fuel pump is attached to fuel sender assembly and is designed to provide fuel at a pressure above the pressure needed by the fuel injectors. A fuel pressure regulator, attached to fuel rail, keeps fuel available to fuel injectors at a regulated pressure. Unused fuel is returned to fuel tank by a separate fuel return pipe.

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

1. 2 - This step verifies that the fuel pump is operating.
2. 4 - This step tests for an internal fuel leak. If the fuel pressure drops during this test, then an internal loss of pressure is indicated.
3. 6 - This step tests the fuel pressure regulator. The fuel pressure regulator is controlled by engine vacuum. With engine vacuum applied, pressure should drop the specified value.
4. 9 - This step inspects the fuel pressure regulator for a fuel leak from the vacuum port. If fuel leaks from the fuel pressure regulator while fuel pump is commanded ON, replace fuel pressure regulator.
5. 10 - This step tests for a loss of fuel pressure between the fuel feed pipe shut off adapter and fuel pump.
6. 11 - This step tests for a leaking fuel injector or fuel pressure regulator. If fuel pressure remains constant during this test, fuel injectors are not leaking fuel.
7. 14 - This step tests for a restricted fuel return pipe. If fuel pressure is within the specified values, a restriction in the fuel return pipe is indicated.
8. 16 - This step determines if fuel pressure regulator or fuel pump is the cause of the low fuel pressure. If pressure rises above the specified value, fuel pump is okay.
9. 18 - This step verifies that a circuit condition is not the cause of a fuel pressure concern. Inspect all fuel pump electrical circuits thoroughly.

1. Perform diagnostic system check. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-155075-S24848794192003060600000) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 3.4L AZTEK & RENDEZVOUS article. After performing diagnostic system check, go to next step.
2. Turn ignition on, with engine off. Using scan tool, command fuel pump on. Does the fuel pump operate? If yes, go to next step. If no, diagnose fuel pump electrical circuit. See «FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSIS»(ref-153136-S34895118782003041400000) under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 3.4L AZTEK & RENDEZVOUS article.
3. Turn ignition off. Turn off all accessories. Install Fuel Pressure Gauge (J-34730-1A) and Fuel Pressure Gauge Fitting Adapter (J-34730-262). Turn ignition on, with engine off. Using scan tool, command fuel pump (fuel pump runs for about 2 seconds) in order to obtain the highest possible fuel pressure. DO NOT start engine. Observe fuel pressure gauge with fuel pump commanded on. Is fuel pressure within 52-59 psi (358-405 kPa)? If yes, go to next step. If no, go to step 12 .
4. Monitor fuel pressure gauge for one minute. Does the fuel pressure drop more than 5 psi (34 kPa)? If yes, go to step 9 . If no, go to next step.
5. Relieve fuel pressure to 10 psi (69 kPa). Monitor fuel pressure gauge for 5 minutes. Does fuel pressure drop more than 2 psi (14 kPa)? If yes, go to step 24 . If no, go to next step.
6. Turn ignition off for 15 seconds. Turn ignition on, with engine off. Monitor fuel pressure gauge. Start engine. Does fuel pressure drop by 3-10 psi (21-69 kPa) when engine is started? If yes, go to next step. If no, go to step 8 .
7. Operate the vehicle within the conditions of the customers concern. Monitor fuel related parameters with a scan tool. Do any of the scan tool parameters indicate a lean condition? If yes, go to step 17 . If no, see «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-155075-S24848794192003060600000) under SELF-DIAGNOSTICS - 3.4L AZTEK & RENDEZVOUS article.
8. Disconnect vacuum hose from fuel pressure regulator. Monitor fuel pressure gauge. Operate engine at idle. Using a hand-held vacuum pump, apply 12-14 in. Hg (34-47 kPa) to fuel pressure regulator. Does fuel pressure drop to 3-10 psi (21-69 kPa) when vacuum is applied? If yes, go to step 21 . If no, go to step 23 .
9. Turn ignition off. Remove vacuum hose from fuel pressure regulator. Turn ignition on, with engine off. Using scan tool, command fuel pump on. Inspect for fuel leak from fuel pressure regulator vacuum port. Is fuel pressure regulator leaking fuel? If yes, go to step 23 . If no, go to next step.
10. Turn ignition off. Relieve fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE»(ref-152619-S00388317402003021700000) . Disconnect fuel feed hose and fuel return hose from fuel rail pipes. Install a Fuel Line Shut-Off Adapters (J-37287) between fuel hoses and the fuel rail pipes. Open valves on fuel pipe shut-off adapters. Turn ignition on, with engine off. Command fuel pump on using scan tool. Obtain highest possible fuel pressure. Bleed air from fuel pressure gauge. Close fuel feed pipe shut-off valve. Monitor fuel pressure gauge for one minute. Does fuel pressure remain constant? If yes, go to step 19 . If no, go to next step.
11. Turn ignition off. Open fuel feed pipe shut-off valve. Turn ignition on, with engine off. Command fuel pump ON and then OFF with scan tool. Close fuel return pipe shut-off valve. Monitor fuel pressure gauge for one minute. Does the fuel pressure remain constant? If yes, go to step 23 . If no, go to step 20 .
12. Is fuel pressure greater than 59 psi (427 kPa)? If yes, go to step 14 . If no, go to next step.
13. Is fuel pressure greater than zero psi? If yes, go to step 16 . If no, go to step 17 .
14. Turn ignition off. Relieve fuel pressure. Disconnect fuel return hose from fuel rail return pipe. Attach a length of flexible fuel hose to fuel rail outlet passage. Place open end of the flexible fuel hose into an approved gasoline container. Turn ignition on, with engine off. Using scan tool, monitor fuel pressure gauge while fuel pump is operating. Is fuel pressure within 52-59 psi (358-405 kPa)? If yes, go to step 22 . If no, go to next step.
15. Inspect the fuel rail return pipe and fuel rail outlet passage for a restriction. Did you find and correct the condition? If yes, go to step 25 . If no, go to step 23 .
16. Turn ignition off. Relieve fuel pressure. Disconnect fuel return hose from fuel rail return pipe. Install a Fuel Line Shut-Off Adapters (J-37287) between fuel return pipe and fuel rail. Open valve in the fuel pipe shut-off adapter. Turn ignition on, with engine off. Bleed air from fuel system. Monitor fuel pressure gauge. DO NOT allow fuel pressure to exceed 75 psi (517 kPa). Excessive pressure may damage fuel system. Slowly close valve in fuel return pipe shut-off adapter. Command fuel pump on with scan tool. Does the fuel pressure rise to greater than 52 psi (358 kPa)? If yes, go to step 23 . If no, go to next step.
17. Inspect fuel filter and fuel feed pipe for restriction. Did you find and correct the condition? If yes, go to step 25 . If no, go to next step.
18. Inspect the harness connectors and ground circuits of the fuel pump for poor connections. Did you find and correct the condition? If yes, go to step 25 . If no, go to next step.
19. Remove the fuel sender assembly. Inspect fuel pump flex hose for damage, fuel pump harness connectors for poor connections, fuel strainer for a restriction or contaminates in fuel tank Did you find and correct the condition? If yes, go to step 25 . If no, go to step 24 .
20. Turn ignition off. Raise fuel rail with fuel lines connected. Turn ignition on, with engine off. Command fuel pump on with scan tool. Locate and replace the leaking fuel injector. After repairs, go to step 25 .
21. Repair vacuum source to fuel pressure regulator. After repairs, go to step 25 .
22. Locate and repair restricted fuel return line. After repairs, go to step 25 .
23. Replace fuel pressure regulator. After replacing fuel pressure regulator, go to step 25 .
24. Replace fuel pump. After replacing fuel pump, go to next step.
25. Operate the system in order to verify the repair. Did you correct the condition? If yes, system is okay. If no, go to step 3 .