Engine Controls - System/component Tests Cadillac Catera I

MODEL IDENTIFICATION

Vehicle model is identified by fourth character of Vehicle Identification Number (VIN). VIN is stamped on metal pad on top of left end of instrument panel, near windshield.

INTRODUCTION

Before testing separate components or systems, perform all procedures listed in BASIC TESTING article. Since many computer-controlled and monitored components will set a diagnostic trouble code if they malfunction, it is also recommended self-diagnosis be performed. See TESTS W/CODES article.

Note. Testing individual components does not isolate shorts or opens. Perform all voltage tests with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure. Use ohmmeter to isolate wiring harness shorts or opens.

MULTI-RAM SYSTEM DIAGNOSIS

Note. Powertrain Control Module (PCM) may also be referred to as Engine Control Module (ECM).

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 article.
2. Connect scan tool to data link connector. Retrieve DTCs. If DTCs do not exist, go to next step. If DTCs exist, perform appropriate DTC test. See TESTS W/CODES article.
3. Visually inspect system. Check for disconnected or damaged vacuum hoses and/or components. Check linkage between vacuum actuators and valves for binding or interference with hoses. Ensure wiring is routed properly and not damaged. If problem does not exist, go to next step. If problem exist, repair as necessary, then go to step 14).
4. Start engine and observe vacuum actuator linkages for switchover valves. Using scan tool, command each valve on and off. If both valves operate, go to next step. If both valves do not operate, go to step 6).
5. Turn ignition switch to LOCK position. Remove duct from between intake resonance switchover valve and throttle body. Hold throttle plates open to view moveable divider in back of intake manifold. Move actuator linkage by hand and ensure divider moves with linkage. Look down passages in intake resonance switchover valve to view moveable divider between 2 sides of valve. Move actuator linkage by hand to ensure divider moves with linkage. If both valves operate properly, system is okay. If either valve does not operate, go to step 13).
6. Using scan tool, exit device control. Disconnect manifold vacuum supply hose at solenoid valve while observing actuator linkage. If actuator does not move when vacuum is disconnected, go to next step. If actuator moves when vacuum is disconnected, replace solenoid valve, then go to step 10).
7. Check for vacuum at manifold vacuum supply hose. If vacuum exists, go to next step. If vacuum does not exist, go to step 11).
8. Disconnect other hose from solenoid valve and connect hoses together using suitable vacuum connector. If actuator linkage does not operate, go to next step. If linkage operates, go to step 10).
9. Disconnect vacuum hoses from actuator. If vacuum exists, go to step 13). If vacuum does not exist, go to step 12).
10. Replace solenoid valve and go to step 14).
11. Repair vacuum supply hose or plugged vacuum source and go to step 14).
12. Repair vacuum hose to actuator and go to step 14).
13. Replace valve/actuator assembly and go to step 14).
14. Start engine. Observe vacuum actuator linkages for switchover valves. Using scan tool, command each valve on and off. If both valves operate, system is okay. If both valves do not operate, go to step 2).

Ground Circuits

1. Using an ohmmeter, check for continuity to ground at PCM ground terminals. See «POWERTRAIN CONTROL MODULE (PCM) CONNECTOR I.D.»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. Resistance should be zero ohms. If not, repair open to ground.
2. Using a voltmeter, connect negative lead of voltmeter to a good ground. Backprobe positive lead of voltmeter to each ground terminal. With vehicle running, voltmeter should indicate less than one volt. If voltmeter reading is more than one volt, check for open, short to voltage, corrosion or loose connection on ground circuit.

Power Circuits

1. Using a voltmeter, check for battery voltage between PCM continuous power terminal(s) and ground. See «POWERTRAIN CONTROL MODULE (PCM) CONNECTOR I.D.»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) table. If battery voltage is not present, check for blown fuse or open fusible link. If okay, check for open in wire between PCM terminal and power source.
2. Turn ignition switch to RUN position. Using a voltmeter, check for battery voltage between PCM ignition power terminals and ground. If battery voltage is not present, check IGN fuse. If fuse is okay, check for an open in wire between battery and ignition switch, and between ignition switch and PCM terminal. If okay, check for a defective ignition switch.
3. Connect voltmeter between ground and PCM starter (crank) signal terminal. On vehicles with manual transmission/transaxle, depress clutch pedal. On vehicles with automatic transmission/transaxle, position gear shift lever in Park. On all vehicles, turn ignition switch to START position. Battery voltage should be present only when ignition switch is in START position.
4. If voltage is not present, check CRANK fuse or fusible link between ignition switch and PCM terminal. If fuse or fusible link is okay, check for an open in wire between ignition switch and PCM terminal, or check for a defective ignition switch.

PCM Harness Resistance

Turn ignition switch to LOCK position. Disconnect PCM and appropriate component harness connectors. Check for open or short circuits between PCM harness connector terminal and component harness connector terminal. See POWERTRAIN CONTROL MODULE (PCM) CONNECTOR I.D. table. See WIRING DIAGRAMS article. If harness is open or shorted, repair as necessary.

Scheme 1

POWERTRAIN CONTROL MODULE (PCM) CONNECTOR I.D. (1)

DIAGNOSTIC TROUBLE CODES

TROUBLE CODE DEFINITION

ENGINE SENSORS & SWITCHES

Note. For additional sensor testing specifications, see SENSOR RANGE CHARTS article.

Manufacturer does not provide many individual system and component testing. For sensor and switch testing not listed, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODES in TESTS W/CODES article.

MOTORS, RELAYS & SOLENOIDS

Manufacturer does not provide many individual system and component testing. For motor, relay and solenoid testing not listed, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODES under COMPUTERIZED ENGINE CONTROLS. See TESTS W/CODES article.

Idle Air Control (IAC) Motor

See IDLE CONTROL SYSTEM.

A/C Clutch Relay

See A/C-HEATER SYSTEM article in AIR CONDITIONING & HEAT section.

Fuel Pump Relay

See BASIC TESTING article.

SOLENOIDS

All PCM-controlled solenoids should have at least 20 ohms of resistance when checked with positive ohmmeter lead connected to power supply terminal of solenoid and negative ohmmeter lead connected to ground terminal of solenoid. Some solenoids are equipped with internal diodes. On these solenoids, resistance values will differ if ohmmeter test leads are reversed.

FUEL SYSTEM

Note. For fuel system pressure testing, see BASIC TESTING article.

Manufacturer does not provide many individual system and component testing. For fuel system testing not listed, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODES in TESTS W/CODES article.

Note. Retrieve DTCs and perform appropriate DTC test before performing FUEL INJECTOR CIRCUIT DIAGNOSIS. See TESTS W/CODES article. Also ensure all mechanical and ignition coil/module circuit malfunctions are repairs before performing FUEL INJECTOR CIRCUIT DIAGNOSIS.

IDLE CONTROL SYSTEM

Note. For idle control system testing, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODES in TESTS W/CODES article.

IGNITION SYSTEM

Note. For basic ignition system checks, see BASIC TESTING article.

For ignition system testing not listed, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODES in TESTS W/CODES article.

EMISSION SYSTEMS & SUB-SYSTEMS

Note. For emission and sub-system testing not listed, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODES in TESTS W/CODES article.

EVAP CONTROL SYSTEM DIAGNOSIS

Note. Ensure all vacuum line and EVAP system components are not damaged or missing before proceeding with this test.

AIR Pump (Belt-Driven)

Accelerate engine to approximately 1500 RPM and observe airflow from hoses. If airflow increases as engine is accelerated, pump is working properly. If airflow does not increase, check hoses, pump belt tension, leaky valves or defective air injection pump.

Check Valve

Detach check valve and blow through valve in direction of check valve flow (to cylinder head). Attempt to suck air back. Replace valve if airflow is allowed against the direction of flow.

EXHAUST GAS RECIRCULATION

Manufacturer does not provide many individual system and component testing. For EGR system testing not listed, perform related DTC testing procedure. See DIAGNOSTIC TROUBLE CODES in TESTS W/CODES article.

Exhaust System Check

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»(/cadillac/catera/i-1996-2001/remont/testing-diagnostics/#engine-control-system-tests-wcodes) article.
2. Remove heated oxygen sensor. Install exhaust backpressure tester in place of oxygen sensor. Start engine and let idle. If pressure reading is not 1.25 psi or greater, go to next step. If pressure reading is 1.25 psi or greater, go to step 4).
3. Increase engine speed to 2000 RPM. If pressure reading is greater than 3 psi, go to next step. If pressure reading is not greater than 3 psi, go to step 6).
4. Check exhaust system for crushed pipe, internal muffler damage or heat distress. If problem does not exist, go to next step. If problem exists, repair as necessary and go to step 6).
5. Replace catalytic converter and go to next step.
6. Operate vehicle within conditions under which original symptom was noted. If system operate properly, system is okay at this time. If system does not operate properly, go to step 2).

Required Service

The PCV system may require service for obstructions if any of the following conditions exist

1. Rough idle.
2. Stalling or slow idle speed.
3. Oil leaks.
4. Oil in air cleaner.
5. Sludge in engine.

A leaking PCV valve or hose could cause

1. Rough idle.
2. Stalling.
3. High idle speed.

If engine idles rough, check for clogged PCV valve or plugged or broken hoses BEFORE adjusting idle. Check PCV valve application to ensure correct valve is fitted. Replace PCV valve if required.

Checking PCV Valve Function

1. Remove PCV valve from rocker cover. Run engine at idle. Place thumb over open end of valve to check for vacuum. If there is no vacuum at valve, check for obstruction in manifold port, hoses or PCV valve. Repair or replace as necessary.
2. Turn engine off. Remove PCV valve. Shake valve and listen for rattle of check valve inside. If a clear rattle is not heard, replace PCV valve.
3. Visually inspect valve for varnish or deposits which may make PCV valve operation sticky or restricted, or cause incomplete seating of valve. Replace if necessary.
4. An engine must be sealed for PCV system to function as designed. If leakage, sludging or dilution of oil is noted and PCV system is functioning properly, check engine for cause and repair as required to ensure PCV system will continue to function properly.
5. An engine operating without any crankcase ventilation can be damaged, so it is important to replace PCV valve and air cleaner breather (if equipped) at regular intervals (at least every 30,000 miles). Check all hoses and clamps for failure or deterioration.

MISCELLANEOUS CONTROLS

Note. Although some of the controlled devices listed here are not technically engine performance components, they can affect driveability if they malfunction.

TRANSMISSION

Note. Computerized transmission controls are also covered in greater detail in TRANSMISSION SERVICING - A/T article in AUTOMATIC TRANS SERVICE section for domestic vehicles. For component circuit identification, see wiring diagram in WIRING DIAGRAMS article.

Converter Clutch Solenoid

Disconnect harness connector to Torque Converter Clutch (TCC) solenoid. Measure resistance between appropriate TCC solenoid terminals. Solenoid resistance should be greater than 20 ohms.

Note. Some solenoids may have an internal pressure switch in series with the solenoid winding and will not show continuity until that pressure switch is applied by transmission hydraulic pressure.

Converter Lock-Up Signal At Transmission

1. Warm engine to operating temperature. Raise vehicle and support drive wheels. Support suspension where necessary to prevent damage to drive axles.
2. Disconnect converter clutch connector at transmission. Connect a test light across appropriate converter clutch harness terminals. Start engine and place transmission in Drive. Accelerate vehicle to 45 MPH and note test light.
3. If test light is off, check solenoid power supply wire of harness for open or short to ground. Check ground circuit for open between harness connector and PCM. If harness is okay, see CONVERTER LOCK-UP SIGNAL FROM PCM.

Converter Lock-Up Signal From PCM

1. Warm engine to operating temperature. Raise vehicle and support drive wheels. Support suspension where necessary to prevent damage to drive axles.
2. Connect a test light to battery voltage. Touch TCC control driver terminal with test light. Accelerate vehicle to 45 MPH and note test light. If test light does not illuminate, problem is a faulty PCM connector or PCM.

PCM CONTROLLED GENERATOR

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 article.
2. Turn ignition switch to RUN position. If charging light illuminates, go to next step. If charging light does not illuminate, go to step 4).
3. Start engine. If charging light does not go out, go to step 5). If charging light goes out, go to step 21).
4. Turn ignition switch to LOCK position. Disconnect generator harness connectors. Turn ignition switch to RUN position. If charging light illuminates, go to step 6). If charging light does not illuminate, go to step 7).
5. Turn ignition switch to LOCK position. Connect scan tool to data link connector. Turn ignition switch to RUN position. Ensure all accessories are off. Observe generator voltage on scan tool. If battery voltage is displayed, go to step 8). If less than battery voltage is displayed, go to step 9).
6. Using a test light connected to ground, probe charging light signal circuit at generator harness connector. If test light illuminates, go to step 10). If test light does not illuminate, go to step 11).
7. Replace or repair instrument cluster and/or charging light bulb as necessary. After repairs are complete, go to step 21).
8. Using scan tool, check GEN F valve. If 5 percent is displayed, go to step 7). If 5 percent is not displayed, go to step 12).
9. Turn ignition switch to LOCK position. Disconnect generator harness connectors. Turn ignition switch to RUN position. Using a test light connected to battery voltage, probe charging light signal circuit at generator harness connector. If test light illuminates, go to step 13). If test light does not illuminate, go to step 14).
10. Locate and repair short to ground in charging light control signal circuit and go to step 21).
11. Replace generator and go to step 21).
12. Turn ignition switch to LOCK position. Disconnect generator harness connectors. Turn ignition switch to RUN position. Using a test light connected to battery voltage, probe generator field circuit at generator harness connector. If test light illuminates, go to step 15). If test light does not illuminate, go to step 16).
13. Locate and repair short to ground in field circuit and go to step 21).
14. Measure voltage at charging light signal circuit at generator harness connector. If 4.5 volts or greater exists, go to step 17). If 4.5 volts or greater does not exist, go to step 18).
15. Locate and repair short to ground in field circuit. After repairs are complete, go to step 21).
16. Locate and repair poor connection and/or open in field circuit. After repairs are complete, go to step 21).
17. Measure voltage at battery voltage supply circuit at generator harness connector. If battery voltage exist, go to step 11). If battery voltage does not exist, go to step 19).
18. Check for poor connection and/or open in battery voltage supply circuit. If poor connection and/or open does not exist, go to step 20). If poor connection and/or open exists, repair as necessary and go to step 21).
19. Locate and repair poor connection and/or open in battery voltage supply circuit. After repairs are complete, go to step 21).
20. Replace PCM and go to next step.
21. Operate vehicle under condition under which original symptom was noted. If system does not operate properly, go to step 2).

A/C COMPRESSOR CLUTCH CONTROLS

Note. For A/C clutch circuit testing, see A/C-HEATER SYSTEM article in the AIR CONDITIONING & HEAT section. See wiring diagram in WIRING DIAGRAMS article for terminal and wire color identification.

When A/C button on A/C-heater control panel is pressed, an A/C request signal is sent through the refrigerant pressure switch and Engine Control Module (ECM) to the coil of A/C clutch relay (K60). The A/C clutch relay is located at left front of engine compartment, in ECM housing. This enables A/C clutch relay to energize, allowing ignition voltage to energize compressor clutch coil and fan control relay (K87).

When fan control relay energizes, battery voltage is supplied to auxiliary cooling fan No. 1, and through the normally open contacts of fan control relay (K52), to auxiliary cooling fan No. 2. If coolant temperature reaches 248°F (120°C), secondary temperature switch contacts will open and the compressor clutch coil is disengaged, causing A/C system to turn off. Secondary temperature switch will not allow A/C system to turn back on until coolant temperature has dropped to 239°F (115°C) or less.

Compressor clutch coil can also be turned off by refrigerant pressure switches (low pressure switch or high pressure switch). Low pressure switch will turn compressor clutch off as soon as refrigerant pressure falls to about 26 psi (1.8 kg/cm 2 ). This is done by opening the low pressure switch contacts and not allowing battery voltage to pass through A/C clutch relay (K60) to compressor clutch coil. Low pressure switch activates the compressor clutch when refrigerant pressure increases to about 36.3 psi (2.6 kg/cm 2 ).

High pressure switch will turn compressor clutch off as soon as refrigerant pressure exceeds about 435 psi (30.6 kg/cm 2 ). This is done by opening the high pressure switch contacts in refrigerant pressure switch and not allowing battery voltage to pass through A/C clutch relay (K60) to compressor clutch. High pressure switch activates compressor clutch when refrigerant pressure drops to less than about 290 psi (19.3 kg/cm 2 ).

When refrigerant pressure exceeds about 159.4 psi (11.2 kg/cm 2 ), A/C control switch contacts will close and engine idle speed will increase to compensate for RPM drop that occurs when A/C system is switched on. A/C control switch is installed in high pressure line, between A/C compressor and condenser. When refrigerant pressure drops to less than about 130.5 psi (9.2 kg/cm 2 ), A/C control switch contacts will close and allow engine idle speed to return to normal.

ELECTRIC COOLING FAN CONTROL

Note. For electric cooling fan circuit testing, see ENGINE COOLING FAN article in ENGINE COOLING section. See wiring diagram in WIRING DIAGRAMS article for terminal and wire color identification.

Electric cooling fan circuits consist of one engine cooling fan, 2 auxiliary cooling fans, 2 temperature switches, A/C pressure switch, Engine Control Module (ECM) cooling blower, timing control pump, auxiliary water pump, 5 fan control relays, one ECM relay, one auxiliary water pump relay and one engine cooling fan resistor. Relays are located at left front of engine compartment, in ECM housing. Auxiliary water pump is provided with battery voltage with ignition on, and when coolant temperature reaches 194°F (90°C).

At 212°F (100°C), primary temperature switch stage one contacts will close, enabling ECM relay (K48) and cooling fan control relay (K26) to energize. When ECM relay energizes, ignition voltage is applied to ECM cooling blower, allowing it to operate.

When cooling fan control relay (K26) energizes, battery voltage is applied to auxiliary cooling fan No. 1 and to auxiliary cooling fan No. 2 through the normally open contacts of fan control relay (K52). This allows auxiliary cooling fans to operate in series at half speed.

Fan control relay (K26) supplies battery voltage to engine cooling fan through the engine cooling fan resistor. The engine cooling fan resistor limits engine cooling fan operation to half speed. Fan control relay (K26) will also supply battery voltage to timing control pump through normally closed contacts of the auxiliary water pump relay (K22). This will allow timing control pump to operate.

Primary temperature switch stage one contacts will open when coolant temperature reaches 203°F (95°C). This will turn on all 3 fans, ECM cooling blower and turn the timing control pump off, unless A/C system is on.

If ignition switch is off and coolant temperature is greater than 212°F (100°C), both auxiliary cooling fans, engine cooling fan and timing control pump will remain on until coolant temperature drops to less than 203°F (95°C).

If temperature reaches 221°F (105°C), temperature switch contacts will close enabling fan control relays (K52 and K28) to energize. When fan control relay (K52) energizes, auxiliary cooling fan No. 1 runs at full speed as it is no longer in series with auxiliary cooling fan No. 2. When fan control relay (K28) energizes, battery voltage is applied to auxiliary cooling fan No. 2 which runs at full speed.

With primary temperature switch stage one contacts closed, ECM cooling blower, timing control pump and engine cooling fan (half speed) will continue to operate. Secondary temperature switch contacts will open when coolant temperature reaches 212°F (100°C) and cause operation of auxiliary cooling fans to operate differently as designated by primary temperature switch.

If coolant temperature reaches 230°F (110°C), secondary temperature switch stage two contacts will close, enabling fan control relay (K67) to energize. When fan control relay (K67) energizes, battery voltage is applied directly to engine cooling fan causing it to run at full speed. All other operations that were taking place before coolant temperature reached 230°F (110°C) remain in effect. Primary temperature switch stage two contacts open when coolant temperature reaches 221°F (105°C) and engine cooling fan will return to half speed.

At coolant temperatures greater than about 230°F (110°C), all 3 cooling fans run at full speed. ECM cooling blower, timing control pump and auxiliary water pump are also operating. Only 6 of the 7 relays operate at this time, unless A/C system is on. In this case, fan control relay (K87) and A/C clutch relay (K60) will also operate.

To prevent excessively high refrigerant pressure, auxiliary cooling fans are switched from first speed to second speed at refrigerant pressures greater than about 276 psi (19.4 kg/cm 2 ). When pressure drops to less than about 218 psi (15.3 kg/cm 2 ), auxiliary cooling fans are switched back to first speed.

COMPONENT LOCATIONS

Note. Component location illustrations are not available at time of publication.

COMPONENT LOCATIONS (VIN R) BODY

See also:
• TESTS W/CODES
• POWERTRAIN CONTROL MODULE (PCM) CONNECTOR I.D.