Engine Controls - System/component Tests: Diagnosis Pontiac Bonneville IX

A/C ON (A/C REQUEST) SWITCH TEST

1. Start engine and allow to idle. If a scan tester is available, scan A/C request parameter. Move A/C mode selector back and forth between ON and OFF positions. Scan status should change.
2. If scan tester is not available or scan status does not change, measure voltage between ground and PCM A/C request terminal. For wiring schematics, see mini-schematics under A/C CLUTCH (C-10) & ELECTRIC COOLING FAN (C-12) under «MISCELLANEOUS CONTROLS»(ref-19889-S05054319452001010200000).
3. With A/C mode selector in the ON position, battery voltage should be present. If battery voltage is not present, check for open between A/C mode select switch and PCM A/C request terminal, low A/C refrigerant level causing low pressure switch to open, bad A/C fuse or bad A/C mode select switch.

Injector Balance Test (C-2)

The injector balance test is used to pulse the injector for a precise amount of time, spraying a measured amount of fuel in the intake manifold. As each injector is pulsed, a drop in fuel rail pressure occurs. This pressure drop can be recorded and compared to other injectors. An injector with a pressure drop of 1.5 psi (.11 kg/cm 2 ) or more, greater than or less than other injectors, should be considered faulty.

Note. Allow engine to cool down to avoid irregular readings due to "hot soak" fuel boiling. To prevent flooding, the INJECTOR BALANCE TEST should not be repeated more than once without starting and running engine.

1. Ensure engine is at normal operating temperature. Connect Fuel Pressure Gauge (J-34730-1) to pressure test port. Energize fuel pump using fuel pump test connector or Tech 1 scan tester.
2. Bleed air from fuel gauge and hose to ensure accurate gauge reading. Repeat this procedure until all air is bled from system. Run fuel pump and note fuel pressure. Fuel pressure should be as specified. See «FUEL PRESSURE RANGE»(ref-19889-S36589698352001010200000). If fuel pressure range is not as specified, see BASIC FUEL SYSTEM CHECKS in «BASIC TESTING»(ref-19935) article in this section.
3. Turn fuel pump off. When fuel pump stops, pressure may slightly drop then should hold steady. If fuel pressure does not hold steady, refer to BASIC FUEL SYSTEM CHECKS in «BASIC TESTING»(ref-19935) article in this section.
4. Install Fuel Injector Tester (J-39021) to an injector. Set amperage supply selector switch to "Balance Test, 0.5-2.5 amp." position. Cycle fuel pump on and off to pressurize fuel system. Record stabilized fuel pressure.
5. Depress "Push To Start Test" button on fuel injector tester to energize injector. Note fuel pressure the instant fuel gauge needle stops. Record fuel pressure reading. Perform the same test to all injectors.
6. To obtain pressure drop values, subtract second pressure reading from first pressure reading on each injector. Add all pressure drop values and divide by number of injectors to obtain an average pressure drop.
7. Retest an injector that appears faulty. Replace any injector with a 1.5 psi (.11 kg/cm 2 ) difference, either greater than or less than the average pressure drop. If injectors are all okay, remove test equipment, plug in disconnected harness connectors and review SYMPTOMS in «TESTS W/O CODES»(ref-19937) article in this section.

FUEL PRESSURE RANGE CHART

Fuel Injector Leak Test

1. Turn engine off. Relieve fuel pressure. Access fuel injectors. Connect Fuel Injector Tester (J-39021) to vehicle battery and to a fuel injector. If coolant temperature is 50-95°F (10-35°C), go to next step. If coolant temperature is not 50-95°F (10-35°C), go to step 5).
2. Set fuel injector tester's amperage supply selector switch to "Coil Test 0.5 amp" position. Connect a Digital Volt-Ohmmeter (DVOM) to fuel injector tester. Set DVOM to tenths scale (0.0).
3. Ensure engine coolant temperature is 50-95°F (10-35°C). Press "Push To Start" tester button. Observe DVOM. Voltage reading may climb during test. Record lowest voltage displayed immediately after activation.
4. Perform voltage reading on all injectors. If voltage reading is erratic or falls out of specified range, perform injector balance test or replace faulty injector. See «INJECTOR TEST VOLTAGE RANGE»(ref-19889-S17544504212001010200000) or INJECTOR BALANCE TEST (C2).
5. Press "Push To Start" button on fuel injector tester. Observe DVOM. Voltage reading may climb during test. Record lowest voltage displayed immediately after activation. Perform voltage reading at least twice on all injectors.
6. If voltage reading is erratic or is greater than 9.5 volts, replace affected fuel injector. If voltage reading is not erratic or not greater than 9.5 volts, go to next step.
7. From recorded voltages (except readings greater than 9.5 volts), identify highest voltage reading and subtract from the other recorded voltages. If subtracted value is greater than 0.6 volts, replace affected fuel injector. If subtracted value is less than 0.6 volts, perform injector balance test. See INJECTOR BALANCE TEST (C2).

INJECTOR TEST VOLTAGE RANGE

System Test (Vacuum Operated)

Start and run engine to normal operating temperature. With engine at idle, push up on underside of EGR diaphragm. RPM should drop as EGR valve is opened. If RPM does not drop, remove EGR valve and check for blocked EGR passages. If RPM drops as diaphragm is lifted and EGR vacuum supply is regulated by an PCM-controlled solenoid, verify vacuum is available to solenoid at 2000 RPM and check solenoid using appropriate procedure. See appropriate EGR CONTROL SOLENOID procedure.

CHART C-12A, COOLING FAN CIRCUIT DIAGNOSIS (1 OF 4)

Right cooling fan (fan No. 1) is a low speed fan. Left cooling fan (fan No. 2) is a low and high speed fan. Power for fan motor goes through a 40-amp fusible link to terminal No. 87 of fan relays. Fan relays are energized when a ground circuit is completed through Powertrain Control Module (PCM) quad-driver No. 4. PCM energizes right cooling fan (fan No. 1) relay through PCM terminal WD11 when Engine Coolant Temperature (ECT) sensor indicates 212°F (100°C) or when A/C is requested. PCM energizes left cooling fan (fan No. 2) relay if A/C refrigerant pressure reaches 210 psi (14.8 kg/cm 2 ) or ECT sensor indicates 226°F (108°C).

Note. Test numbers refer to numbers on diagnostic charts.

1. Selecting Tech 1 miscellaneous tests, FAN 1, causes PCM to ground circuit No. 335. Right cooling fan (fan No. 1) should run.
2. Selecting Tech 1 miscellaneous tests, FAN 2, allows control of circuit No. 473. Left cooling fan (fan No. 2) should run.
3. When jumpering A/C head pressure switch harness connector, PCM should operate left cooling fan (fan No. 2) on high speed.

Diagnostic Aids

An intermittent may be caused by a poor connection, rubbed-through wire insulation or a wire broken inside the wire insulation. Check PCM harness connector for backed-out terminals. Connect a DVOM between affected terminal and ground. Wiggle related wires and connectors while watching DVOM for a voltage reading change. Ensure ECT sensor is not mis-scaled. See Diagnostic Trouble Code (DTC) P0118 chart in TESTS W/CODES article in this section. Ensure engine cooling system functions properly.

Scheme 85

Scheme 86

CHART C-10A, A/C COMPRESSOR CLUTCH CIRCUIT DIAGNOSIS (1 OF 3) MANUAL A/C-HEATER

Powertrain Control Module (PCM) delays A/C compressor clutch engagement momentarily after A/C is turned on. This delay allows Idle Air Control (IAC) motor to adjust engine RPM before A/C compressor clutch engages. PCM also disengages A/C compressor clutch during Wide Open Throttle (WOT). A/C compressor clutch is energized when PCM grounds circuit No. 459. PCM may engage A/C compressor clutch during engine cranking.

Note. Test numbers refer to numbers on diagnostic chart.

1. A/C compressor clutch should not be engaged with engine running if an A/C mode is not selected at control head.
2. A/C compressor clutch should apply if conditions under NOTICE at top of chart are met.
3. Checks for an A/C request signal from control head to pressure cycling switch.

Scheme 87

Scheme 88

CHART C-10A, A/C COMPRESSOR CLUTCH CIRCUIT DIAGNOSIS (2 OF 3) MANUAL A/C-HEATER

Note. Test numbers refer to numbers on diagnostic chart.

1. Checks for ignition voltage on circuit No. 639 and PCM control of ground circuit No. 459 to A/C compressor clutch relay coil.
2. Checks for ignition voltage on circuit No. 639 to A/C compressor clutch relay contacts.
3. Determines whether A/C compressor clutch relay, compressor clutch coil or circuitry is faulty.

Scheme 89

CHART C-10A, A/C COMPRESSOR CLUTCH CIRCUIT DIAGNOSIS (3 OF 3) MANUAL A/C-HEATER

Note. Test numbers refer to numbers on diagnostic chart.

1. Determines if PCM is turning A/C compressor clutch relay on due to a false A/C request signal.
2. Determines whether problem is in A/C control head and circuits No. 604 and 762 to pressure cycling switch, or circuit No. 204 and PCM.
3. Checks for circuit No. 59 shorted to battery voltage or a faulty A/C compressor clutch.
4. Determines if A/C compressor clutch relay is faulty or A/C compressor clutch relay control circuit No. 459 is grounded at all times.

Scheme 90

CHART C-10B, A/C COMPRESSOR CLUTCH CIRCUIT DIAGNOSIS (1 OF 3) AUTOMATIC A/C-HEATER

Powertrain Control Module (PCM) delays A/C compressor clutch engagement momentarily after A/C is turned on. This delay allows Idle Air Control (IAC) motor to adjust engine RPM before A/C compressor clutch engages. PCM also disengages A/C compressor clutch during Wide Open Throttle (WOT). A/C compressor clutch is energized when PCM grounds circuit No. 459. PCM may engage A/C compressor clutch during engine cranking.

Note. Test numbers refer to numbers on diagnostic chart.

1. Determines whether or not PCM recognizes the A/C request signal.
2. Checks for an open high pressure cut-out switch.
3. Ensures that A/C-heater control programmer is supplying the A/C request signal.

Scheme 91

Scheme 92

CHART C-10B, A/C COMPRESSOR CLUTCH CIRCUIT DIAGNOSIS (2 OF 3) AUTOMATIC A/C-HEATER

Note. Test numbers refer to numbers on diagnostic chart.

1. Determines whether A/C relay can be controlled by PCM.
2. Checks for ignition voltage to A/C relay contacts.
3. Determines whether problem is caused by A/C relay, relay connections, compressor clutch or compressor clutch circuit is at fault.

Scheme 93

CHART C-10B, A/C COMPRESSOR CLUTCH CIRCUIT DIAGNOSIS (3 OF 3) AUTOMATIC A/C-HEATER

Note. Test numbers refer to numbers on diagnostic chart.

1. Determines if PCM is turning A/C compressor clutch relay on due to a false A/C request signal.
2. Isolates problem to A/C control head and circuits No. 66 and 604 to pressure cycling switch, or circuit No. 204 and PCM.
3. Checks for circuit No. 59 shorted to battery voltage or a faulty A/C compressor clutch.
4. Determines if A/C compressor clutch relay is faulty or A/C compressor clutch relay control circuit No. 459 is grounded all the time.

Scheme 94

Scheme 95

Scheme 96

3.8L (VIN K, L & 1) PCM Wiring Diagram (1 Of 3). Scheme 97

3.8L (VIN K, L & 1) PCM Wiring Diagram (2 Of 3). Scheme 98

3.8L (VIN K, L & 1) PCM Wiring Diagram (3 Of 3). Scheme 99

See also:
• SENSOR RANGE CHARTS
• ADJUSTMENTS