Engine Control System & Engine Component Tests - 4.3L: Diagnosis Oldsmobile Bravada II

DIAGNOSTIC TROUBLE CODES

TROUBLE CODE DEFINITION

Engine Oil Level Sensor/Switch Diagnosis

1. If powertrain OBD system check has been performed, go to next step. If powertrain OBD system check has not been performed, perform powertrain OBD system check. See POWERTRAIN OBD SYSTEM CHECK in «TESTS W/CODES»(ref-33422) article.
2. Using scan tool, observe engine oil level display. If scan tool does not display OK, go to next step. If scan tool displays OK, check for poor connections at sensor and PCM. If poor connection exists, repair as necessary. If poor connection does not exist, perform warning light diagnosis. See PCM CONTROLLED WARNING LIGHTS & GAUGES under «MISCELLANEOUS PCM/VCM CONTROLS»(ref-131391-S42340577812001121900000) .
3. Turn ignition switch to LOCK position. Disconnect PCM harness connectors. Using a test light connected to battery voltage, probe oil level switch signal (Brown wire) at PCM harness connector. If test light does not illuminate, go to next step. If test light illuminates, go to step 7).
4. Ensure ignition switch is in LOCK position. Connect PCM harness connectors. Turn ignition switch to RUN position. Raise and support vehicle. Disconnect oil level switch harness connector. Measure voltage between oil level switch harness connector terminals. If battery voltage does not exist, go to next step. If battery voltage exists, go to step 8).
5. Measure voltage at oil level signal circuit (Brown wire) at oil level switch harness connector. If battery voltage exists, go to next step. If battery voltage does not exist, go to step 9).
6. Check oil level switch signal circuit (Brown wire) for open, between PCM and oil level switch harness connectors. If open exists, repair as necessary and go to step 12). If open does not exist, check for poor connections at sensor and PCM. If poor connection exists, repair as necessary. If poor connection does not exist, perform warning light diagnosis. See PCM CONTROLLED WARNING LIGHTS & GAUGES under «MISCELLANEOUS PCM/VCM CONTROLS»(ref-131391-S42340577812001121900000) .
7. Check for poor connections at PCM. If poor connection exists, repair as necessary and go to step 12). If poor connection does not exist, go to step 11).
8. Check for poor connections at oil level sensor. If poor connection exists, repair as necessary and go to step 12). If poor connection does not exist, go to step 10).
9. Locate and repair open in oil level sensor ground circuit (Black/White wire). After repair are complete, go to step 12).
10. Replace oil level switch and go to step 12).
11. Replace PCM and go to next step.
12. Start engine and allow to warm to normal operating temperature. Turn ignition switch to LOCK position. Allow engine to cool for 15 minutes. Turn ignition switch to RUN position. Using scan tool, observe oil level display. If scan tool does not display OK, go to step 3). If scan tool displays OK, system is okay at this time.

Fuel Injector Circuit Diagnosis

1. If powertrain OBD system check has been performed, go to next step. If powertrain OBD system check has not been performed, perform powertrain OBD system check. See POWERTRAIN OBD SYSTEM CHECK in «TESTS W/CODES - 4.3L»(ref-33422) article.
2. Turn ignition switch to LOCK position. Disconnect fuel injector harness connectors. Using a test light connected to ground, probe appropriate injector ignition feed circuit at injector harness connector. Turn ignition switch to RUN position. If test light illuminates, go to next step. If test light does not illuminate, go to step 7).
3. Connect Fuel Injector Test Light (J-34730-350) to fuel injector harness connectors one at a time. Crank engine while observing test light. If test light does not flash at each injector, go to next step. If test light flashes at each injector, perform inject coil test. See INJECTOR COIL TEST.
4. If fuel injector test light illuminates constantly while engine is being cranked, go to next step. If fuel injector test light does not illuminate constantly while engine is being cranked, go to step 6).
5. Install fuel injector test light on affected circuit. Turn ignition switch to LOCK position. Disconnect PCM/VCM harness connectors. Turn ignition switch to RUN position. If test light illuminates, go to step 8). If test light does not illuminate, go to step 11).
6. Check injector control circuit for open or short to voltage between PCM and injector harness connectors. If open or short exists, go to next step. If open or short does not exist, go to step 9).
7. Repair open or short to voltage in injector control circuit between PCM and injector harness connectors. After repairs are complete, go to step 12).
8. Repair short to ground in injector control circuit, between PCM and injector harness connectors. After repairs, go to step 12).
9. Check PCM/VCM harness connectors for poor connections. If poor connection exists, go to next step. If poor connection does not exist, go to step 11).
10. Repair connections as necessary and go to step 12).
11. Replace PCM/VCM and go to next step.
12. Using scan tool, clear DTCs. Attempt to start engine. If engine starts and continues to run, go to next step. If engine does not start and continue to run, go to step 2).
13. Let engine idle until normal operating temperature is obtained. Retrieve DTCs. If no DTCs are present, system is okay at this time. If any DTCs are present, perform appropriate DTC test. See «TESTS W/CODES - 4.3L»(ref-33422) article.

Injector Balance Test

1. If powertrain OBD system check has been performed, go to next step. If powertrain OBD system check has not been performed, perform powertrain OBD system check. See POWERTRAIN OBD SYSTEM CHECK in «TESTS W/CODES - 4.3L»(ref-33422) article.
2. If injector coil test has been performed, go to next step. If injector coil test has not been performed, perform injector coil test. See INJECTOR COIL TEST.
3. If engine coolant temperature is greater than 201°F (94°C), go to next step. If engine coolant temperature is not greater than 201°F (94°C), go to step 5).
4. Allow engine to cool to less than 201°F (94°C) and go to next step.
5. Install fuel pressure gauge. Turn ignition switch to RUN position then to LOCK position. Bleed air from fuel pressure gauge. Using scan tool, energize fuel pump. If fuel pressure reading is 60-66 psi (4.2-4.6 kg/cm 2 ). If fuel pressure reading is not within specification, perform fuel system diagnosis. See «BASIC TESTING - 4.3L»(ref-124321) article.
6. Turn fuel pump off. Observe fuel pressure gauge. If fuel pressure remains constant, go to next step. If fuel system does not remain constant, perform fuel system diagnosis. See «BASIC TESTING - 4.3L»(ref-124321) article. NOTE: Perform step 7) on each injector.
7. Disconnect fuel injectors harness connector. Using Fuel Injector Adapter (J-34730-3A), connect Fuel Injector Tester (9J-39021) to fuel injector. Connect fuel injector tester power leads to appropriate battery terminals. Set amperage supply selector switch on fuel injector tester to Balance Test 0.5-2.5 amp position. Turn ignition switch to RUN position then to LOCK position. Record fuel pressure reading (first reading). Energize injector by depressing PUSH TO START TEST button on injector tester and hold until fuel pressure gauge stabilizes. Record fuel pressure reading (second reading). Subtract first reading from second reading (this result is pressure drop valve). Add pressure drop valve for each injector together and divide total by 4. If any injector's drop valve is greater or less than average drop valve by 1.5 psi (.1 kg/cm 2 ), replace faulty injector(s) as necessary. If no injector's drop valve is greater or less than average drop valve by 1.5 psi (.1 kg/cm 2 ), injector balance test is okay at this time.

Injector Coil Test

1. If powertrain OBD system check has been performed, go to next step. If powertrain OBD system check has not been performed, perform powertrain OBD system check. See POWERTRAIN OBD SYSTEM CHECK in «TESTS W/CODES - 4.3L»(ref-33422) article.
2. Turn ignition off. Relieve fuel pressure. Connect Fuel Injector Tester (J-39021) to battery voltage. Connect Injector Switch Box (J-39021-210). Set amperage on fuel injector tester to 0.5 amp. Connect DVOM to fuel injector tester. Connect scan tool to data link connector and monitor engine coolant temperature. If coolant temperature is 50-95°F (10-35°C), go to step 4). If coolant temperature is not as specified, go to next step.
3. Allow engine to warm or cool as necessary. If engine coolant temperature is now 50-95°F (10-35°C), go to next step.
4. Using fuel injector tester, press PUSH TO START TEST button and monitor DVOM reading. Perform this test to each injector. Voltage reading should be 5.44-7.53 volts. If voltage reading is as specified, go to next step. If voltage reading is not as specified, perform injector balance test. See INJECTOR BALANCE TEST.
5. Replace faulty injector nozzle and poppet assembly and then proceed to next step.
6. Using scan tool, clear DTCs. Start engine. If engine starts and continues to run, go to next step. If engine does not start or starts and dies, go to step 2).
7. Warm engine to normal operating temperature. Using scan tool, retrieve DTCs. If DTC(s) exists, perform appropriate DTC(s) test. See «TESTS W/CODES - 4.3L»(ref-33422) article. If DTC(s) do not exist, system is okay at this time.

Idle Air Control (IAC) System Diagnosis)

1. If powertrain OBD system check has been performed, go to next step. If powertrain OBD system check has not been performed, perform powertrain OBD system check. See POWERTRAIN OBD SYSTEM CHECK in «TESTS W/CODES - 4.3L»(ref-33422) article.
2. Turn ignition switch to LOCK position. Connect IAC Driver (J-37027-A) to IAC valve. Set parking brake and block wheels. Turn A/C off. Start engine and let idle. Using scan tool, display RPM. Extend and retract IAC valve using IAC driver. If engine RPM changes, go to next step. If engine RPM does not change, go to step 7).
3. If RPM changes smoothly with each flash of IAC driver between 700 and 1500 RPM, go to next step. If RPM does not change smoothly with each flash of IAC driver between 700 and 1500 RPM, go to step 7).
4. Disconnect IAC driver. Check resistance between appropriate IAC valve terminals. See «IAC VALVE RESISTANCE»(ref-131391-S17948649342001121900000) table. (Scheme 4) If resistance is as specified, go to next step. If resistance is not as specified, replace IAC valve and go to step 10). IAC VALVE RESISTANCE Terminals No. Ohms 1 & 2 40-80 1 & 4 Infinity 2 & 3 Infinity 3 & 4 40-80
5. Check harness between PCM and IAC valve harness connector for opens and shorts. If open or shorts do not exist, go to next step. If open or shorts exist, repair as necessary and go to step 10).
6. Check the following: mechanical malfunction, vacuum leaks, lean or rich mixture, poor connection at PCM, defective PCV valve, A/C compressor circuit for short to ground, poor connection at IAC valve or IAC valve passages for blockage or restrictions. If problem does not exist, go to step 9). If problem exists, repair as necessary and go to step 10).
7. Check IAC passages for blockage or restrictions. If blockage or restrictions do not exist, go to next step. If blockage or restrictions exist, repair as necessary and go to step 10).
8. Replace IAC valve and go to step 14).
9. Replace PCM and go to next step.
10. Connect IAC Driver (J-37027-A) to IAC valve. Start engine. Using IAC driver, extend and retract IAC valve. If RPM does not change as expected, go to step 3). If RPM changes as expected, system is okay at this time.

Scheme 4

EGR System Diagnosis

1. If powertrain OBD system check has been performed, go to next step. If powertrain OBD system check has not been performed, perform powertrain OBD system check. See POWERTRAIN OBD SYSTEM CHECK in «TESTS W/CODES - 4.3L»(ref-33422) article.
2. Set parking brake and block wheels. Connect scan tool to data link connector. Start engine and let idle until normal operating temperature is obtained. Using scan tool, command EGR pintle position to zero percent. Increase engine speed to 2000 RPM. If EGR pintle position is now less than 3 percent, go to next step. If EGR pintle position is now greater than 3 percent, go to step 14).
3. Using scan tool, command EGR pintle position to 100 percent in 10 percent increments. Observe MAP sensor and actual EGR pintle position at each increment. EGR pintle should increase by 25 percent or commanded value and MAP sensor value should also increase. If the actual EGR position is within 25 percent of commanded value within 3 seconds, go to next step. If the actual EGR position is not within 25 percent of commanded value within 3 seconds, go to step 6).
4. Using scan tool, set EGR pintle position to 25 percent. If MAP sensor value increases, go to next step. If MAP sensor value does not increase, go to step 13).
5. Using scan tool, command EGR pintle position to 100 percent. If actual EGR pintle position is 100 percent, go to step 15). If actual EGR pintle position is not 100 percent, go to step 14).
6. Check fuses. If fuses are okay, go to next step. If any fuse(s) is blown, repair as necessary and go to step 15).
7. Check EGR valve circuits for opens between PCM and EGR valve harness connectors. If open does not exist, go to next step. If open exists, repair as necessary and go to step 15).
8. Check for poor connection at EGR valve. If poor connection does not exist, go to next step. If poor connection exists, repair as necessary and go to step 15).
9. Measure voltage at EGR valve reference voltage circuit (Red wire) at EGR valve harness connector. (Scheme 5) If 5 volts exists, go to next step. If 5 volts does not exist, go to step 11).
10. Turn ignition switch to RUN position. Remove EGR valve, leaving harness connector attached. Push EGR pintle in and hold pintle in. Using a voltmeter, backprobe sensor signal circuit (Brown wire) at EGR valve harness connector. If no voltage exists, go to next step. If any voltage exists, go to step 14).
11. Check EGR valve pintle signal circuit (Brown wire) for open between PCM and EGR valve harness connector. If open does not exist, go to next step. If open exists, repair as necessary and go to step 15).
12. Replace PCM. Program PCM, perform VTD password relearn procedure and perform crankshaft variation learn procedure. After repair is complete, go to step 15).
13. Clean EGR passages and go to step 15).
14. Replace EGR valve and go to next step.
15. Turn ignition switch to RUN position. Using scan tool, command EGR valve on then off. If EGR valve operates properly, system is okay at this time. If EGR valve does not operate properly, go to step 2).

Scheme 5

EVAP Control System Diagnosis (Enhanced System)

1. If powertrain OBD system check has been performed, go to next step. If powertrain OBD system check has not been performed, perform powertrain OBD system check. See POWERTRAIN OBD SYSTEM CHECK in «TESTS W/CODES - 4.3L»(ref-33422) article.
2. Retrieve DTCs. If DTC P0446, P0452 or P0453 does not exist, go to next step. If DTC P0446, P0452 or P0453 exists, perform appropriate DTC test. See «TESTS W/CODES - 4.3L»(ref-33422) article.
3. Turn ignition switch to LOCK position. Remove gas cap. Turn ignition switch to RUN position. Observe fuel tank pressure on scan tool. If -1-1 in. H2O exists, go to next step. If -1-1 in. H2O does not exist, perform FUEL TANK PRESSURE SENSOR DIAGNOSIS.
4. Install gas cap. Connect Enhanced Pressure Purge Diagnosis Tester (J-41413) to EVAP service port. Using scan tool, command EVAP vent valve on. Attempt to pressurize EVAP system to 5 in. H2O. If EVAP system pressurizes and holds pressure, go to next step. If EVAP system does not pressurize and hold pressure, go to step 6).
5. Maintain 5 in. H2O in EVAP system by turning rotary switch on tester to HOLD position. Observe fuel tank pressure on scan tool. If 5 in. H2O does not exist, go to step 8). If 5 in. H2O exists, go to step 9).
6. Disconnect fuel tank vapor line and EVAP purge line from EVAP canister. Plug EVAP canister fuel tank vapor port. Connect vacuum pump to EVAP canister purge port. Using scan tool, ensure EVAP vent valve is still commanded on. Attempt to apply 5 in. Hg to EVAP canister. If 5 in. Hg can not be obtained or held, go to next step. If 5 in. Hg can be obtained and held, go to step 12).
7. Leave system connected as described in step 6). Disconnect vent line at EVAP canister vent valve. Plug disconnected line. Attempt to apply 5 in. Hg to EVAP canister. If 5 in. Hg cannot be obtained or held, go to step 11). If 5 in. Hg can be obtained and held, go to step 17).
8. Disconnect fuel tank vapor line from EVAP canister. Using enhanced EVAP pressure purge diagnostic tester, attempt to pressurize EVAP system to 5 in. H2O. If 5 in. H2O cannot be obtained and held with pressure applied, go to step 15). If 5 in. H2O can be obtained and held, go to step 18).
9. Disconnect purge line at EVAP canister. Connect vacuum gauge to disconnected line. Start engine and let idle. Using scan tool, command EVAP purge solenoid to 100 percent while observing vacuum gauge. If 12 in. H2O or greater does not exist, go to next step. If 12 in. H2O or greater exists, check the following and repair as necessary: Poor connection at PCM. Misrouted, damaged or disconnected vacuum line. Missing or damaged EVAP system components. Poor connections at EVAP system components.
10. Disconnect purge line from EVAP purge solenoid valve. Connect vacuum gauge to disconnected line. Start engine and let idle. Using scan tool, command EVAP purge solenoid to 100 percent while observing vacuum gauge. If 12 in. H2O or greater does not exist, go to step 16). If 12 in. H2O or greater exists, go to step 14).
11. Check vent hose for possible cause of a vacuum leak. If vacuum leak does not exist, go to step 18). If leak exists, repair as necessary and go to step 19).
12. Check for the following: missing or defective gas cap, disconnected or leaking fuel tank vapor lines or disconnect or damaged EVAP purge line. If problem exists, repair as necessary and go to next step. If problem does not exist, go to step 19).
13. Using scan tool, command EVAP vent valve on. Using enhanced EVAP pressure purge diagnostic tester, pressurize EVAP system to 15 in. H2O. Find leak in EVAP system and repair as necessary. After repair is complete, go to step 19).
14. Repair restriction in EVAP purge line and go to step 19).
15. Repair restriction in EVAP fuel tank vapor line and go to step 19).
16. Replace EVAP canister purge solenoid valve and go to step 19).
17. Replace EVAP canister vent valve and go to step 19).
18. Replace EVAP canister and go to next step.
19. Turn ignition switch to RUN position. Using scan tool, turn EVAP vent valve on. Using enhanced EVAP pressure purge diagnostic tester, pressurize EVAP system to 15 in. H2O. Turn rotary switch on tester to HOLD position. If pressure decreases to less than 10 in. H2O within 2 minutes, go to step 2). If pressure does not decrease to less than 10 in. H2O within 2 minutes, go to next step.
20. Clear DTCs. Using scan tool, perform SERVICE BAY TEST for EVAP system. If scan tool does not display any DTCs, system is okay at this time. If scan tool displays any DTCs, perform appropriate DTC test. See «TESTS W/CODES - 4.3L»(ref-33422) article.

EVAP Control System Diagnosis (Non-Enhanced System)

1. If powertrain OBD system check has been performed, go to next step. If powertrain OBD system check has not been performed, perform powertrain OBD system check. See POWERTRAIN OBD SYSTEM CHECK in «TESTS W/CODES - 4.3L»(ref-33422) article.
2. Start engine and let idle until engine coolant temperature is greater than 113°F (45°C). Ensure vacuum source is okay, repair as necessary. Disconnect outlet line from EVAP purge solenoid. Connect vacuum gauge to EVAP purge solenoid outlet port. Increase engine speed to 2000 RPM. Using scan tool, command EVAP purge solenoid on. If vacuum does not exist, go to next step. If vacuum exist, go to step 6).
3. Disconnect EVAP purge solenoid harness connector. Connect a test light between EVAP purge solenoid harness connector terminals. Using scan tool, command EVAP purge solenoid on. If test light does not illuminate, go to next step. If test light illuminates, go to step 7).
4. Using a test light connected to ground, probe EVAP purge solenoid ignition feed circuit (Pink wire) at EVAP purge solenoid harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 8).
5. Using a test light connected to battery voltage, probe EVAP purge solenoid control circuit (Dark Green/White wire) at EVAP purge solenoid harness connector. Using scan tool, command EVAP purge solenoid on. If test light illuminates, go to step 9). If test light does not illuminate, go to step 10).
6. Check EVAP purge valve vacuum lines. If problem exists, repair as necessary and go to step 13). If problem does not exist, system is okay at this time.
7. Check for poor connection at EVAP purge valve. If poor connection does not exist, go to step 11). If poor connection exists, repair as necessary and go to step 13).
8. Repair open in EVAP purge valve ignition feed circuit (Pink wire), between EVAP purge valve and ENG 1 fuse. After repairs are complete, go to step 13).
9. Repair open in EVAP purge valve control circuit (Dark Green/White wire), between PCM and EVAP purge valve. After repairs are complete, go to step 13).
10. Check for poor connection at PCM. If poor connection does not exist, go to step 12). If poor connection exists, repair as necessary and go to step 13).
11. Replace EVAP purge valve and go to step 13).
12. Replace PCM. Program PCM, perform VTD password relearn procedure and perform crankshaft variation learn procedure. See «COMPUTER RELEARN PROCEDURES»(ref-33335) article in GENERAL INFORMATION. After repair is complete, go to next step.
13. Turn ignition switch to RUN position. Using scan tool, command EVAP purge solenoid on then off. If EVAP purge valve operate as expected, system is okay at this time. If EVAP purge valve does not operate as expected, go to step 2).

Fuel Tank Pressure Sensor Diagnosis

1. If powertrain OBD system check has been performed, go to next step. If powertrain OBD system check has not been performed, perform powertrain OBD system check. See POWERTRAIN OBD SYSTEM CHECK in «TESTS W/CODES - 4.3L»(ref-33422) article.
2. Disconnect fuel tank pressure sensor harness connector. Measure voltage at reference signal circuit (Gray wire) at fuel tank pressure harness connector. If about 5 volts does not exist, go to next step. If about 5 volts exists, go to step 5).
3. Check for poor connection at PCM. If poor connection does not exist, go to next step. If poor connection exists, go to step 12).
4. Check fuel tank pressure sensor reference voltage circuit (Gray wire) for open between PCM and fuel tank pressure sensor harness connector. If open does not exist, go to step 9). If open exists, go to step 11).
5. Remove gas cap. Using 2 fused jumper wires, connect reference voltage and signal circuits between fuel tank sensor and fuel tank pressure sensor harness connector. Measure voltage at ground terminal at fuel tank pressure sensor. If 1.3-1.7 volts exist, go to next step. If 1.3-1.7 volts do not exist, go to step 14).
6. Check fuel tank pressure sensor signal circuit (Dark Blue wire) for poor connection at PCM. If poor connection does not exist, go to next step. If poor connection exist gas cap. Using 2 fused jumper wires, connect reference voltage and signal circuits between fuel tank sensor and fuel tank pressure sensor harness connector. Measure voltage at ground terminal at fuel tank pressure sensor. If 1.3-1.7 volts exists, go to next step. If 1.3-1.7 volts does not exist, go to step 14).
7. Check fuel tank pressure sensor signal circuit (Dark Blue wire) for poor connection at PCM. If poor connection does not exist, go to next step. If poor connection exists, go to step 12).
8. Check fuel tank pressure sensor signal circuit (Dark Blue wire) for open and short between PCM and fuel tank pressure harness connectors. If open or short exists, go to step 13). If open or short does not exist, go to step 15).
9. Check fuel tank pressure sensor ground circuit (Black wire) for poor connection at PCM. If poor connection does not exist, go to next step. If poor connection exists, go to step 12).
10. Check fuel tank pressure sensor ground circuit (Black wire) for open between PCM and fuel tank pressure harness connectors. If open exists, go to step 13). If open does not exist, go to step 15).
11. Repair open in fuel tank pressure sensor reference voltage circuit (Gray wire), between PCM and fuel tank pressure sensor harness connectors. After repair are complete, perform EVAP CONTROL SYSTEM DIAGNOSIS.
12. Repair connections as necessary and perform EVAP CONTROL SYSTEM DIAGNOSIS.
13. Repair open or short as necessary and perform EVAP CONTROL SYSTEM DIAGNOSIS.
14. Replace fuel tank pressure sensor and perform EVAP CONTROL SYSTEM DIAGNOSIS.
15. Replace PCM. Program PCM, perform VTD password relearn procedure and perform crankshaft variation learn procedure. See «COMPUTER RELEARN PROCEDURES»(ref-33335) in GENERAL INFORMATION.

Warning Light Diagnosis

1. If powertrain OBD system check has been performed, go to next step. If powertrain OBD system check has not been performed, perform powertrain OBD system check. See POWERTRAIN OBD SYSTEM CHECK in «TESTS W/CODES - 4.3L»(ref-33422) article.
2. Check instrument cluster system. See «INSTRUMENT PANEL»(ref-33551) article in ACCESSORIES/SAFETY EQUIP section. If problem exists, repair as necessary. If problem does not exist, go to next step.
3. Turn ignition switch to LOCK position. Disconnect PCM harness connectors. Turn ignition switch to RUN position. Using a DVOM, check voltage between affected PCM output circuit at PCM harness connector terminal and ground. See «POWERTRAIN CONTROL MODULE (PCM)»(ref-131391-S37823730892001121900000) table under COMPUTERIZED ENGINE CONTROLS. See appropriate wiring diagram in «WIRING DIAGRAMS - 4.3L»(ref-128589) article. If battery voltage exists, go to next step. If battery voltage does not exist, go to step 7).
4. Set DVOM to 10-amp scale. Check current between affected PCM output circuit and ground. Monitor reading for about 2 minutes. If 0.05-1.50 amps exists, go to step 12). If 0.05-1.50 amps does not exist, go to next step.
5. Disconnect instrument cluster harness connectors, leaving PCM harness connectors disconnected. Check voltage between affected PCM output circuit and ground. If zero volts exists, go to step 15). If zero volts does not exist, go to next step.
6. Locate and repair short to voltage in affected PCM output circuit. After repairs, go to step 17).
7. Check ignition feed fuse for instrument cluster indicator lights. If fuse is blown, go to next step. If fuse is okay, go to step 9).
8. Locate and repair short to ground in ignition feed circuit for instrument cluster indicator lights. Replace fuse and go to step 17).
9. Disconnect instrument cluster connector. Turn ignition on. Check voltage between ignition feed circuit for instrument cluster indicator lights and ground. If battery voltage exists, go to next step. If battery voltage does not exist, go to step 14).
10. Check affected PCM output circuit for an open or shorted circuit to ground. If open or short exists, go to step 17). If open or short does not exist, go to next step.
11. Check affected PCM output circuit and ignition feed circuit for poor connection at instrument cluster and at PCM. If poor connection exists, repair as necessary and go to step 17). If poor connection does not exist, go to step 15).
12. Turn ignition switch to LOCK position. Reconnect PCM harness connector. Disconnect instrument cluster connector. Turn ignition on. Connect a test light between affected PCM output circuit and ignition feed circuit at instrument panel harness connector. Using a scan tool, perform OUTPUTS TEST function to cycle affected warning light on and off. If test light illuminates as expected, check for shorted component or circuit in the output driver circuit. Check for faulty instrument cluster. If test light does not illuminate as expected, go to next step.
13. Check affected PCM output circuit for poor connection to PCM. If problem exists, repair as necessary and then go to step 17). If problem does not exist, go to step 16).
14. Repair open in ignition feed circuit to instrument cluster indicator lights. After repairs, go to step 17).
15. Replace instrument cluster and then go to step 17).
16. Replace PCM and then go to next step.
17. Using scan tool, operate affected warning light. If warning light does not operate properly, go to step 3).

Tachometer Control Circuit Diagnosis

1. Diagnose instrument cluster. See «INSTRUMENT PANEL»(ref-33551) article in ACCESSORIES/SAFETY EQUIP section. After diagnosis, go to next step.
2. Perform powertrain On-Board Diagnostic (OBD) system check. See POWERTRAIN OBD SYSTEM CHECK in «TESTS W/CODES - 4.3L»(ref-33422) article. After performing OBD system check, go to next step.
3. Turn ignition off. Disconnect PCM connector. Turn ignition on. Using a DVOM, check voltage between tachometer control circuit at PCM harness connector terminal and ground. See appropriate wiring diagram in «WIRING DIAGRAMS - 4.3L»(ref-128589) article. Battery voltage should be present. If battery voltage is present, go to next step. If battery voltage was not present, go to step 7).
4. Set DVOM to 10-amp scale. Check current between tachometer control circuit and ground. Monitor reading for about 2 minutes. DVOM should read .05-1.50 amps. If reading is not as specified, go to next step. If reading is as specified, go to step 12).
5. Disconnect instrument cluster, leaving PCM connector disconnected. Using DVOM, check voltage between tachometer control circuit and ground. DVOM should read zero volts. If voltage reading is as specified, go to step 15). If voltage reading is not as specified, go to next step.
6. Locate and repair short to voltage in tachometer control circuit. After repairs, go to step 17).
7. Check ignition feed fuse for instrument cluster. If fuse is blown, go to next step. If fuse is okay, go to step 9).
8. Locate and repair short to ground in ignition feed circuit to instrument cluster. Replace fuse and go to step 17).
9. Disconnect instrument cluster connector. Turn ignition on. Check voltage between ignition feed circuit for instrument cluster and ground. Battery voltage should be present. If battery voltage was not present, go to step 14). If battery voltage is present, go to next step.
10. Check tachometer control circuit for an open or shorted circuit to ground. If circuit is open or shorted, go to step 17). If circuit was okay, go to next step.
11. Check tachometer control circuit and ignition feed circuit for poor connection at instrument cluster and at PCM. If problem is present, repair as necessary and then go to step 17). If problem was not found, go to step 15).
12. Turn ignition off. Reconnect PCM harness connector. Disconnect instrument cluster connector. Turn ignition on. Connect a test light between tachometer control circuit and ignition feed circuit at instrument panel harness connector. Using a scan tool, perform OUTPUTS TEST function to cycle tachometer control output light on and off. If test light flashes on and off, check for shorted component or circuit in the output driver circuit. Check for faulty instrument cluster. If test light does flash on and off, go to next step.
13. Check tachometer control circuit for poor connection to PCM. Replace defective terminal and then go to step 17). If terminal is okay, go to step 16).
14. Repair open in ignition feed circuit to instrument cluster. After repairs, go to step 17).
15. Replace instrument cluster and then go to step 17).
16. Replace PCM and then go to next step.
17. Start engine and observe tachometer. If tachometer does not operate properly, diagnose instrument cluster. See «INSTRUMENT PANEL»(ref-33551) article in ACCESSORIES/SAFETY EQUIP section.