Engine Controls - System/component Tests - Efi: Other Isuzu Rodeo I

Trooper DOHC

To check induction air control system, proceed to CHART C-2D. (Scheme 118)and (Scheme 119).

CHART 2D - INDUCTION AIR CONTROL SYSTEM TROOPER DOHC

Note. Test number refer to numbers on diagnostic chart.

1. Without proper vacuum at solenoid, system will not function properly.
2. When ignition is on and engine is not running solenoid should not be energized. Solenoid is normally open; vacuum should pass to actuator.
3. With diagnostic terminal grounded, ECM should ground White/Blue wire, which should energize solenoid to prevent vacuum from passing to actuator.
4. This step checks circuit continuity.

Scheme 118

Scheme 119

Ground Circuits

Using a DVOM, touch negative voltmeter lead to a good ground. Touch positive voltmeter lead to each ground terminal. With vehicle running, voltmeter should indicate less than one volt. If reading is greater than one volt, check for open, corrosion and loose connection on ground lead. See ECM GROUND LOCATION table for ECM ground location.

ECM GROUND LOCATION

Power Circuits (Constant Voltage)

1. ECM should always have constant battery voltage to retain memory. On Amigo, Pickup 2.6L and Rodeo 2.6L, check voltage at Red/White wire of 22-pin ECM connector; on Pickup 3.1L, check voltage at Red wire of 32-pin or White wire of 24-pin ECM connector. Voltage is supplied by fuse No. 3, located in fuse block at left side of dash.
2. On Rodeo 3.2L and Trooper, check voltage at Red/White wires of 24-pin and 32-pin ECM connectors. Voltage is supplied by ECM fuse, located in fuse/relay box at right side of engine compartment.

Power Circuits (Ignition Voltage)

1. ECM should always have battery voltage when ignition is on. On Amigo, Pickup and Rodeo 2.6L, check voltage at Light Green/Red and Light Green/Black wires of 26-pin ECM connector. Voltage is supplied by ECM relay, located in fuse/relay box at right side of engine compartment. White/Blue wire of main relay receives voltage from fuse No. 1 in fuse/relay box at right corner of engine compartment. Violet wire of main relay receives voltage from fuse No. 8, located in fuse block at left side of dash.
2. On Rodeo 3.2L and Trooper, check voltage at Red/Green wire of 24-pin ECM connector. Voltage is supplied by main relay, located on right side of engine compartment. Red/White wire at main relay should have constant battery voltage and Black/Yellow wire should have voltage only if ignition is on. Voltage to Red/White wire is supplied by Black fusible link, located in fusible link box at right front corner of engine compartment.Black/Yellow wire receives voltage from fuse No. 8, located in fuse block on left side under dash.

A/C SWITCH

See A/C CLUTCH CONTROL under MISCELLANEOUS CONTROLS.

AIRFLOW SENSOR

Note. Airflow sensor malfunctions may set Code 61 or 62. For additional information, see appropriate information in TESTS W/CODES - 2.6L article.

Amigo, Pickup & Rodeo 2.6L

1. Pull back rubber boot on airflow sensor harness connector. With ignition off, check for voltage between Violet wire terminal and ground. Voltage should be less than.2 volt. If voltage is incorrect, check wiring to ECM. Repair as necessary.
2. Turn ignition on. With engine off, check voltage between Red wire and ground. Voltage should be 10-14 volts. With ignition off, voltage should be less than.2 volt. If voltage is incorrect, check wiring to ECM. Repair as necessary.
3. With engine idling, check voltage between White wire and ground. Voltage should be 0.5-2.0 volts. If voltage is incorrect and voltage insteps 1) and 2) was okay, replace airflow sensor.
4. Check airflow sensor by-pass circuit. (Scheme 120) If circuit is dirty or contaminated, clean with carburetor cleaner. DO NOT let carburetor cleaner touch electrical or rubber components.

Scheme 120

COOLANT TEMPERATURE SENSOR

Note. Coolant temperature sensor malfunctions may set Code 14 or 15. For additional information, see appropriate TESTS W/CODES - 2.6L article.

1. Unplug coolant temperature sensor. On Amigo, Pickup 2.6L and Rodeo 2.6L, sensor is located on right side of engine, below intake manifold. Sensor connector contains Black and Green/Yellow wires. On Pickup 3.1L, sensor is located at front of engine. Sensor connector contains White and Green/Yellow wires.
2. On all models, check resistance between sensor terminals at specified temperature. See «COOLANT TEMPERATURE SENSOR RESISTANCE SPECIFICATIONS»(ref-16828-S38506141702000122900000) table. Replace sensor if it is not within specification.

COOLANT TEMPERATURE SENSOR RESISTANCE SPECIFICATIONS

CRANKSHAFT POSITION SENSOR

Note. Crankshaft position sensor malfunctions may set Code 42. For additional testing, see appropriate SELF-DIAGNOSTICS article.

If crankshaft position sensor malfunctions, Code 41 will set. See appropriate SELF-DIAGNOSTICS article. Replace distributor assembly if wiring circuit is okay.

Rodeo 3.2L & Trooper

1. Crankshaft position sensor is located on lower right side of engine block, above oil pan. For testing, disconnect crankshaft position sensor connector at DIS module. Using DVOM, probe terminals B1 and B3. Resistance should be 900-1200 ohms.
2. If resistance is as specified, go to step 3). If resistance is not as specified, check wiring to sensor for open or shorts and repair as necessary. If wiring is okay, replace sensor.
3. With DVOM connected as in step 1), set DVOM to 2-volt AC scale and crank engine. Ensure reading is greater than .1 volt.

Pickup 3.1L

To test crank signal, proceed to CHART C-1B. (Scheme 121)and (Scheme 122).

CHART C-1B - CHECKING CRANK SIGNAL PICKUP 3.1L

Crank signal is a 12-volt signal to ECM during cranking to allow enrichment and cancel diagnostics until engine is running or 12-volt signal is no longer on circuit.

1. Checks for normal cranking voltage to ECM terminal C9. Test light should be on during cranking.
2. Checks if source of blown fuse was faulty ECM.

Scheme 121

Scheme 122

Pickup 3.1L & Trooper DOHC

See TIMING CONTROL SYSTEMS under IGNITION SYSTEM.

MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR

Note. A malfunctioning MAP sensor may set Code 33 or 34 (Amigo, Pickup and Rodeo 2.6L) or Code 33A or 33B (Rodeo 3.2L, and Trooper). For additional testing, see appropriate SELF-DIAGNOSTICS article.

On Amigo, Pickup 2.6L and Rodeo 2.6L, sensor is located on right side of engine compartment. On Pickup 3.1L, sensor is located on left side of air cleaner. On Rodeo 3.2L and Trooper SOHC, sensor is located on top right side of engine. On Trooper DOHC, sensor is located on top front of engine to left of throttle body. To diagnose MAP sensor problem, proceed to CHART C-1D. (Scheme 123), (Scheme 124) and (Scheme 125).

CHART C-1D - MAP SENSOR OUTPUT

Note. Test numbers refer to numbers on diagnostic chart.

1. This step checks MAP sensor output voltage to ECM. Without engine running, this voltage represents a barometric reading to ECM.
2. Applying a vacuum reading of 10 in. Hg to MAP sensor should cause voltage to be 1.2-2.3 volts less than voltage in step 1). When applying vacuum to sensor, change in voltage should be instantaneous. A slow voltage change indicates a faulty sensor.
3. This step checks vacuum hoses to sensor for leaks and restrictions. Ensure no other vacuum devices are connected to MAP sensor hose.

Scheme 123

Scheme 124

Scheme 125

MANIFOLD AIR TEMPERATURE (MAT) SENSOR

Note. Malfunctioning MAT sensor may set Code 23A or 23B. For additional testing, see appropriate SELF-DIAGNOSTICS article.

1. Remove MAT sensor from intake manifold. MAT sensor is located near throttle position sensor and contains a Blue/Black and Black/White wire connector.
2. Using ohmmeter, check resistance across sensor terminals. Reading should vary with temperature. Replace sensor if not within specification. See MAT SENSOR RESISTANCE SPECIFICATIONS table.

MAT SENSOR RESISTANCE SPECIFICATIONS

OXYGEN (O2) SENSOR

Note. Malfunctioning O2 sensor may set Code 13, 44 or 45. For additional testing, see TESTS W/CODES - 2.6L article.

1. Start engine, and warm it to operating temperature. Ensure vehicle is operating in closed loop. Unplug O2 sensor connector at sensor. Using Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, connect DVOM (on voltmeter scale) between ground and O2 sensor connector (sensor side).
2. Place a short jumper wire in sensor lead (computer side). While holding jumper wire in one hand, alternately touch negative battery terminal and then positive battery terminal with other hand. DO NOT touch sensor lead directly to battery.
3. Monitor DVOM reading. When negative battery terminal is touched, O2 sensor output voltage should increase (up to one volt). When positive battery terminal is touched, O2 sensor output voltage should drop (as low as.1 volt). If O2 sensor does not respond as indicated, replace sensor. To test O2 sensor heater on Rodeo 3.2L and Trooper, go to CHART C-1F. (Scheme 126)and (Scheme 127).

CHART C-1F - OXYGEN SENSOR HEATER CHECK RODEO 3.2L & TROOPER

Note. Test numbers refer to number on diagnostic chart.

Generator charging circuit supplies battery voltage to heater part of oxygen sensor. Heater warms oxygen sensor to allow a varying voltage to be produced by oxygen sensor.

1. This step will verify battery voltage is present for heater.
2. This step checks ground circuit to heater.
3. This step checks heater element resistance.

Scheme 126

Scheme 127

Disconnect switch connector at transmission. Note terminal identification. (Scheme 128) Using ohmmeter, check continuity between specified terminals in proper gear positions. See PARK/NEUTRAL SWITCH CONTINUITY SPECIFICATIONS table. Replace switch if continuity is not as specified.

PARK/NEUTRAL SWITCH CONTINUITY SPECIFICATIONS

Scheme 128

For park/neutral switch testing procedure, proceed to CHART C-1A. (Scheme 129)and (Scheme 130). Relay is mounted on left side of auto transmission. Switch is also called automatic transmission mode switch.

CHART C-1A - PARK/NEUTRAL SWITCH RODEO 3.2L & TROOPER

Note. Test numbers refer to numbers on diagnostic chart.

1. This step checks for closed switch to ground in Park position and open switch in Drive ranges. ECM supplies voltage to Pink/Blue wire and senses closed switch when voltage drops to less than one volt. ECM uses this input to control idle speed, EGR operation and vehicle speed sensor diagnostics.
2. For access to diode wiring, remove lower cover of underhood fuse/ relay box.

Scheme 129

Scheme 130

Power steering pressure switch is located in power steering pump housing. To test power steering pressure switch, proceed to CHART C-1E. (Scheme 131)and (Scheme 132). Replace switch if defective.

CHART C-1E - POWER STEERING PRESSURE SWITCH RODEO 3.2L & TROOPER

Power Steering Pressure Switch (PSPS) is normally open and circuit No. 901 (Green/Yellow wire) is about battery voltage. When power steering pump pressure increases, PSPS closes, causing voltage on circuit No. 901 (Green/Yellow wire) to fall to less than one volt.

ECM monitors voltage and increase idle speed when voltage decreases. If PSPS fails to close or open exist in circuit No 901 (Green/Yellow wire), engine may stall when power steering pump pressure is high. If PSPS fails to open or short to ground exists in circuit No. 901 (Green/Yellow wire), idle speed may be affected and A/C relay will be de-energized.

1. Check scan tester instructions on how switch state will be displayed.
2. This step checks for a short to ground in circuit No. 901 (Green/Yellow wire).
3. This step simulates a closed switch.

Note. Test numbers refer to numbers on diagnostic chart.

Scheme 131

Scheme 132

THROTTLE POSITION SENSOR (TPS)

Note. Malfunctioning TPS may also set Code 21A or 21B (Rodeo 3.2L, and Trooper) or Code 21 or 22 (Pickup 3.1L). For additional testing, see appropriate TESTS W/CODES - 2.6L article.

Pickup 3.1L, Rodeo 3.2L & Trooper

1. Unplug TPS harness at sensor. Connect ohmmeter between Blue/Orange and Blue/Red wire terminals of sensor for Rodeo 3.2L and Trooper or Blue/Red and Green/Yellow wire terminals of sensor for Pickup 3.1L.
2. Resistance reading should vary smoothly as throttle is moved from idle to wide open throttle. Resistance reading should not drop or climb suddenly as continuity is checked. Replace sensor if defective.
3. To check sensor operating voltage, connect TPS harness. Sensor operating voltage may be monitored at ECM with ignition on. Note ECM location. See «ECM LOCATION»(ref-16828-S32797341952000122900000) table. ECM LOCATION Model Location Pickup & Rodeo Behind Left Kick Panel Trooper Under Instrument Panel
4. Turn ignition on. DO NOT start engine. Using digital voltmeter, backprobe ECM connector terminals to check if 5-volt TPS reference signal exists. Reference signal should exist at following ECM terminals: Pickup 3.1L - C14 (Green/Yellow wire). Rodeo 3.2L & Trooper - A1 (Blue/Orange wire).
5. If 5-volt reference signal is not present, check for short to ground in 5-volt reference line from ECM to TPS. If no short is present, ECM is defective.
6. If 5-volt reference signal is present, test TPS input signal at appropriate ECM terminal. Connect negative voltmeter probe to ground. Backprobe ECM terminal with positive voltmeter probe at following ECM wire terminals: Pickup 3.1L - C13 (Blue/Red wire). Rodeo 3.2L & Trooper - D6 (Blue/Red wire).
7. With engine running, voltage should be about .5 volt at idle and increase to about 5 volts at wide open throttle. If voltage reading is incorrect, check wiring to TPS. If wiring is okay, replace TPS.

1. Disconnect throttle valve switch. Note terminal identification. (Scheme 133) Check throttle valve switch terminals for proper continuity. With throttle at idle, continuity should exist between terminals "I" and "P", but not terminals "P" and "F." 2) At wide open throttle, continuity should exist between terminals "P" and "F", but not terminals "I" and "P." Continuity should not exist between terminals "I" and "P" or "P" and "F" with throttle between idle and wide open position. Replace throttle valve switch if defective.

Scheme 133

Disconnect transmission temperature sensor. Measure resistance across terminals of sensor connector. Replace sensor if resistance is not within specification. See TRANSMISSION TEMPERATURE SENSOR RESISTANCE table.

TRANSMISSION TEMPERATURE SENSOR RESISTANCE

VEHICLE SPEED SENSOR (VSS)

Note. Malfunctioning vehicle speed sensor may set Code 24 or 63. For additional testing, see TESTS W/CODES - 2.6L article.

1. Remove instrument cluster and combination meter from dash. Using ohmmeter, check continuity across VSS terminals. (Scheme 134)
2. Rotate speedometer shaft slowly. Reading should alternate from continuity to an open circuit 4 times per revolution. Replace speedometer assembly if VSS is defective.

Scheme 134

Note. This procedure has been updated per TSB number SB93-04-006 .

1. Vehicles have one VSS mounted on left rear of transmission. Transmission mounted VSS sends signal to speedometer VSS, which controls needle movement and sends signal to ECM and cruise control.
2. For testing transmission mounted VSS, remove VSS from transmission by rotating sensor body. Connect jumper wire between VSS connector terminal 1 and positive battery terminal. (Scheme 135)and (Scheme 136). WARNING: DO NOT connect battery voltage to VSS connector terminal 3; VSS damage will result.
3. Connect jumper wire between VSS connector terminal 2 and negative battery terminal. Connect 1.3k-5k ohm resistor (1/4 watt or more) between VSS connector terminals 1 and 3.
4. Using a DVOM, measure voltage across resistor while rotating sensor shaft slowly. With one rotation of sensor shaft, voltage should fluctuate 4 times. Ensure voltage fluctuates between 10-14 volts and 2 volts or less. If sensor voltage is outside specification, replace VSS.

Scheme 135

Scheme 136

MODULES, MOTORS, RELAYS & SOLENOIDS

Note. For component locations (Scheme 138)- (Scheme 142).

Electronic Spark Control Module

See TIMING CONTROL SYSTEMS under IGNITION SYSTEM.

IAC Motor

This component is called Idle Air Control (IAC) valve. See IDLE CONTROL SYSTEM .

A/C Compressor Relay

See A/C CLUTCH CONTROL under MISCELLANEOUS CONTROLS.

ECM Relay

1. Remove relay from connector. Test for continuity between terminals No. 1 and 2. (Scheme 137) Continuity should exist. Test for continuity between terminals No. 3 and 4. Continuity should not exist.
2. Apply battery voltage between terminals No. 5 and 6. Test for continuity between terminals No. 1 and 2. Continuity should not exist. Test for continuity between terminals No. 3 and 4. Continuity should exist. Replace relay if defective.

Scheme 137

Main Relay

Remove relay from connector. Test for continuity between terminals No. 2 and 4. Continuity should exist. Apply battery voltage between terminals No. 1 and 3. Continuity should not exist between terminals No. 2 and 4. Replace relay if defective. For terminal locations, refer to illustration. see scheme 59

Restart Relay

See STARTER RELAYS under MISCELLANEOUS CONTROLS.

Starter Relay

Starter relay test procedure is same as fuel pump relay procedure. See FUEL PUMP RELAY under FUEL DELIVERY.

Air Regulator Solenoid

See IDLE CONTROL SYSTEM .

Scheme 138

Scheme 139

Scheme 140

Scheme 141

Scheme 142

FUEL DELIVERY

Note. For fuel system pressure testing, see appropriate information in BASIC TESTING - EFI article.

Pressure Regulator

1. Install fuel pressure gauge on fuel rail. Use care when installing fuel pressure gauge, as fuel lines are under pressure. Disconnect vacuum hose at pressure regulator.
2. Start engine and note fuel pressure. Ensure vacuum supply exists at vacuum line. Reconnect vacuum hose. Fuel pressure should decrease slightly. Replace regulator if pressure does not change.

Note. Malfunctioning pressure regulator VSV may set Code 25 or 53. For additional testing, see appropriate SELF-DIAGNOSTICS article.

Pressure Regulator Vacuum Switching Valve (VSV)

1. On Amigo, Pickup and Rodeo 2.6L, VSV is located on right side of engine compartment, near battery. On all models, pressure regulator VSV and canister purge VSV share a 4-pin electrical connector and are mounted side by side. Ensure VSV hoses are connected to pressure regulator.
2. Disconnect electrical connector. Connector contains Black/White and Light Green wires. Wires for pressure regulator VSV are Blue and Black.
3. Using ohmmeter, check resistance between Blue and Black wire terminals of VSV. Replace VSV if resistance is not about 35 ohms. Reconnect connector.
4. To check VSV operation with engine off, disconnect electrical connector. Apply battery voltage to Blue wire, and connect ground wire to Black wire. Replace VSV if operation of vacuum ports does not change. WARNING: Use care when installing fuel pressure gauge, as fuel lines are under pressure.
5. To check VSV operation with engine running, install fuel pressure gauge on fuel rail. Start engine and note fuel pressure. Fuel pressure should be about 35 psi (2.5 kg/cm 2 ). Disconnect electrical connector from VSV.
6. Apply battery voltage to Blue wire, and connect ground wire to Black wire of VSV. Fuel pressure should be about 42 psi (2.9 kg/cm 2 ). Replace VSV if pressure does not increase.

Fuel Pump Relay

1. Fuel pump relay is located under hood on right inner fenderwell inside relay box. Remove relay from connector. Test for continuity between terminals No. 1 and 3. (Scheme 143) Continuity should not be present. Test for continuity between terminals No. 1 and 2. Continuity should be present.
2. Apply battery voltage between terminals No. 4 and 5. Continuity should exist between terminals No. 1 and 3. Continuity should not exist between terminals No. 1 and 2. Replace relay if defective.

Scheme 143

FUEL CONTROL

Note. Throttle valve switch and throttle position sensor are mounted on throttle body throttle shaft. M/T models use throttle valve switch. A/T models use throttle position sensor and throttle valve switch.

Note. Fuel cut-off and fuel injection reactivation is controlled by throttle valve switch. See FUEL-CUT SPECIFICATIONS table for fuel-cut operating conditions.

Fuel-Cut (Slow-Cut) System (Amigo, Pickup & Rodeo 2.6L)

1. Warm engine to operating temperature. Turn ignition off. Unplug throttle valve switch wire connector. Insert a fine wire into upper (idle) terminal. Reconnect throttle valve switch connector with fine wire partially pulled outward. (Scheme 144)
2. Start engine, and operate it at 2000-2500 RPM. Connect battery voltage to fine wire installed on throttle valve switch. When battery voltage is applied, engine speed should decrease to about 1250 RPM. Engine surging may occur, which is normal during test procedure.

FUEL-CUT SPECIFICATIONS

Scheme 144

Fuel Injectors

1. Unplug fuel injector harness at injector. Using ohmmeter, measure resistance across terminals. Replace fuel injectors if resistance is not within specification. See «FUEL INJECTOR RESISTANCE SPECIFICATIONS»(ref-16828-S08174828232000122900000) table.
2. With engine running, check fuel injector operating noise. Normal operation of injectors is indicated if a regular click is heard, which varies with engine speed. If click is not heard, replace injector.

FUEL INJECTOR RESISTANCE SPECIFICATIONS

Note. FUEL INJECTOR BALANCE TEST is also known as CHART C-2A.

See A/C CLUTCH CONTROL under MISCELLANEOUS CONTROLS.

Scheme 145

1. Check operation of air regulator with engine cold. Start engine and note if idle speed is higher than normal after initial start. If idle speed is not higher, proceed to step 4).
2. As engine temperature increases, engine idle speed should stabilize. Check air regulator for leakage. Disconnect hose between air regulator and throttle valve body at throttle valve body side. Plug throttle body fitting end. (Scheme 145)
3. Start engine. Check for variation in engine speed by closing and opening end of air regulator hose. Variation in engine speed should be less than 50 RPM. Replace air regulator if variation in engine speed is more than specification.
4. If fast idle speed was not higher than normal on initial engine start, disconnect air regulator harness connector at air regulator. Air regulator is located on right rear of engine, below intake manifold.
5. Using ohmmeter, measure resistance between air regulator terminals. Resistance should be 45.5-49.5 ohms on Amigo or Pickup or 38-42 ohms on Rodeo. Replace air regulator if resistance is not as specified. If resistance is as specified, go to next step.
6. Turn ignition on. Using a voltmeter, check for voltage at air regulator harness connector. If voltage is present, replace air regulator. If voltage is not present, check wiring to air regulator and fuel pump relay.

IDLE AIR CONTROL VALVE (PICKUP 3.1L)

For Idle Air Control (IAC) valve testing, proceed to CHART C-2C. see scheme 30and see scheme 31.

IDLE AIR CONTROL VALVE (RODEO 3.2L & TROOPER)

1. If Idle Air Control (IAC) valve is operating improperly, remove IAC valve from throttle body. Inspect IAC valve and throttle body bore for binding and clogged passages. Repair as necessary. If binding or clogged passages are not present, proceed to next step.
2. Disconnect electrical connector from IAC valve. Using ohmmeter, check resistance across terminals No. 1 and 2 and across terminals No. 3 and 4. see scheme 32and see scheme 33. Replace valve if resistance is not 40-80 ohms.
3. Using ohmmeter, check continuity across terminals No. 1 and 4 and across terminals No. 2 and 3. Replace IAC valve if continuity exists. If IAC valve tests okay, check for faulty connections at IAC valve and ECM. If connections are okay, check input devices used by ECM to control IAC valve operation. see scheme 32and see scheme 33.

PARK/NEUTRAL SWITCH

See PARK/NEUTRAL SWITCH under ENGINE SENSORS & SWITCHES.

CHART C-2C - IDLE AIR CONTROL VALVE 3.1L PICKUP

Note. Test numbers refer to numbers on diagnostic chart.

1. Continue with test, even if engine will not idle. If idle is too low, scan tester will display 80 or more counts. If idle is high, it will display zero counts. Occasionally, an erratic or unstable idle may occur. Engine speed may vary 200RPM or more up and down. Disconnect IAC valve. If condition is unchanged, IAC is not at fault.
2. When engine was stopped, IAC valve plunger retracted (more air) to a fixed park position for increased air flow and idle speed during next engine start. Scan tester will display 100 or more counts. When performing this test, immediately note RPM on start-up. On a warm engine, RPM will decrease rapidly.
3. ensure IAC valve is disconnected before testing. Test light will confirm ECM signals with a steady or flashing light on all circuits.
4. A circuit may be shorted to voltage, which would be indicated by a steady light. Disconnect ECM, and turn ignition on. Probe terminals to check for this condition.

CHART C-2C - IDLE AIR CONTROL VALVE RODEO 3.2L & TROOPER

Note. Test numbers refer to number on diagnostic chart. For Rodeo and Trooper see WIRING DIAGRAMS article. For testing purposes, IAC connector terminals correspond as follows: "A" is No. 1, "B" is No. 2, "C" is No. 3 and "D" is No. 4.

1. IAC tester is used to extend and retract IAC valve. Valve movement is verified by engine speed change. If engine speed does not change, valve can be retested when removed from throttle body.
2. This step checks quality if IAC movement in step 1). Engine speed should change smoothly with each flash of tester light in both extend and retract positions at 700-1500 RPM. If IAC valve is retracted beyond control range (1500 RPM), it may take many flashes in extend position before engine speed will begin to drop. Fully extending IAC valve may stall engine. This is normal condition.
3. Steps 1) and 2) verify proper IAC operation. This step checks IAC circuits. Each lamp on node light should flash Red and Green while IAC valve is cycled. While sequence of color is not important, check circuits for faults if either light is off or does not flash. Begin with poor terminal connections.

IGNITION SYSTEM

Note. For basic ignition checks, see BASIC TESTING - EFI article.

TIMING CONTROL SYSTEMS

Note. If problem develops with ESC, ECM will set Code 43. For additional testing, see appropriate SELF-DIAGNOSTICS article.

Electronic Spark Control (ESC) (Pickup 3.1L & Trooper DOHC)

To test ESC system, proceed to appropriate CHART C-5. (Scheme 144)and (Scheme 145). On Pickup, ESC module is located on right side fenderwell. On Trooper, ESC module is located under evaporative emission canister. Module has a 5-pin connector.

Electronic Spark Timing (EST) (Pickup 3.1L)

1. To check system operation, check timing at 1500 RPM with ALDL ungrounded. Locate ALDL connector.
2. ALDL is located behind right side of instrument panel below left side of instrument panel on Pickup. (Scheme 146)or (Scheme 147).
3. On Pickup 3.1L, install jumper wire between terminals "A" and "B" of ALDL connector. (Scheme 146) (Scheme 147) Note timing at 1500 RPM. If timing changes, system is operating correctly.

Scheme 146

Scheme 147

CHART C-5 - ESC SYSTEM PICKUP 3.1L

Electronic Spark Control (ESC) is accomplished using an ESC module which sends a voltage signal to ECM. As knock sensor detects engine knock, voltage from ESC module to ECM is shut off, signaling ECM to retard timing (if engine speed is greater than 900 RPM).

Note. Test numbers refer to numbers on diagnostic chart.

1. If Code 43 is not set but knock signal is indicated while running at 1500 RPM, listen for an internal engine noise. Under a no-load condition, detonation should not exist. If a knock is indicated, an internal engine problem may exist.
2. Usually a knock signal can be generated by tapping on right exhaust manifold. This test can also be performed at idle. Test number 1) was run at 1500 RPM to determine if a constant knock signal (which would affect engine performance) was present.
3. This tests whether knock signal is due to sensor, a basic engine problem or ESC module.
4. If module ground circuit is faulty, ESC module will not function correctly. Test light should glow, indicating ground circuit is okay.
5. Contacting terminal "A" of ESC module harness using a test light to 12 volts should generate a knock signal. This will determine whether knock sensor is faulty or if ESC module cannot recognize a knock signal.

CHART C-5 - ESC SYSTEM TROOPER DOHC

Electronic Spark Control (ESC) is accomplished using an ESC module which sends a voltage signal to ECM. As knock sensor detects engine knock, voltage from ESC module to ECM is shut off. This signals ECM to retard timing (if engine speed is greater than 900 RPM).

Note. Test numbers refer to numbers on diagnostic chart.

1. If Code 43 is not set but knock signal is indicated while running at 1500 RPM, listen for an internal engine noise. Under a no-load condition, detonation should not exist. If a knock is indicated, an internal engine problem may exist.
2. Usually a knock signal can be generated by tapping on right exhaust manifold. This test can also be performed at idle. Test number 1) was run at 1500 RPM to determine if a constant knock signal (which would affect engine performance) was present.
3. This tests whether knock signal is due to sensor, a basic engine problem or ESC module.
4. If module ground circuit is faulty, ESC module will not function correctly. Test light should glow, indicating ground circuit is okay.
5. Touching a test light from 12 volts to terminal "E" should generate a knock signal. This will determine whether knock sensor is at fault or ESC module cannot recognize a knock signal.

Air Management Valve (Amigo, Pickup & Rodeo 2.6L)

1. Warm engine to normal operating temperature. With engine idling, ensure secondary air is passing from silencer on air management valve. (Scheme 148)
2. Stop engine. Disconnect air hose at check valve. Plug opening of check valve. Start engine and note air passage from air management valve. After a few seconds, air should pass from silencer. Replace air management valve if defective. Air management valve will operate only under specified conditions. (Scheme 149)

Check Valve (Amigo, Pickup & Rodeo 2.6L)

Remove check valve from air manifold. Blow air into air pump side of check valve. Air should pass freely to manifold side of check valve. Blow air into manifold side of check valve. Air should not pass to air pump side of valve. Replace check valve if defective.

Scheme 148

Scheme 149

Backpressure Transducer (BPT) (Amigo & Pickup 2.6L Federal; Rodeo 2.6L)

Disconnect BPT vacuum hoses. Blow air into Black port (bottom port). Ensure air does not pass through transducer. When blowing on vacuum line to EGR at transducer, ensure air passes through transducer and out air filter. Replace assembly if defective.

Duty Solenoid (Amigo & Pickup 2.6L California)

Apply battery voltage to duty solenoid terminals, and air should flow without restriction between ports "X" and "Y". (Scheme 150) Disconnect battery voltage from terminals and air should not flow through ports. Replace duty solenoid if defective.

EGR System (Amigo & Pickup 2.6L Federal; Rodeo 2.6L)

Testing procedure is not available from manufacturer. System will operate only under specified conditions. (Scheme 151)

Scheme 150

Scheme 151

EGR System (Amigo & Pickup 2.6L California)

1. System will operate only under specified conditions. (Scheme 152) To test system operation, ensure engine coolant temperature is less than 59°F (15°C). Install tachometer. Disconnect vacuum hose at EGR valve, and connect vacuum gauge to vacuum hose.
2. Start engine. Vacuum gauge should read zero at all engine speeds. With engine at normal operating temperature, vacuum gauge should read zero at idle. Vacuum gauge should start to indicate vacuum at 3500 RPM. Reconnect vacuum hose to EGR valve. Ensure EGR valve diaphragm moves when engine is at 2000 RPM.

Scheme 152

Note. Ensure Code 32 or 34 is not stored before testing EGR system. See appropriate SELF-DIAGNOSTICS article.

EGR System (Pickup 3.1L)

EGR solenoid is located inside EGR control module, on rear of right cylinder head. To check EGR system, proceed to CHART C-7. (Scheme 154)and (Scheme 155).

EGR System (Rodeo 3.2L & Trooper)

To check EGR system, proceed to CHART C-7A. see scheme 48and see scheme 49.

EGR Transducer (Rodeo 3.2L& Trooper)

1. Remove vacuum hoses from EGR transducer. Place finger over port "P" (VSV), and blow into port "Q" (EGRV). see scheme 48and see scheme 49. Air should pass through filter of EGR transducer.
2. Place finger over port "P" (VSV), and blow into port "R" (tube "S"). Air should pass through EGR transducer, but be restricted. Replace EGR transducer if defective.

EGR Vacuum Switching Valve (VSV) (Amigo & Pickup 2.6L -CA)

Apply 12 volts to VSV terminals. (Scheme 150) Air should flow freely through ports. Disconnect voltage. Air should not flow through ports. Replace VSV if defective.

EGR Vacuum Switching Valve (VSV) (Rodeo 2.6L)

Apply battery voltage to VSV terminals. Air should flow freely between ports "Y" and "Z" and not between ports "X" and "Y". (Scheme 153) Disconnect voltage. Air should flow between ports "X" and "Y" and not between ports "Y" and "Z". Replace VSV if defective.

Scheme 153

EGR Vacuum Switching Valve (Rodeo 3.2L & Trooper)

1. Disconnect vacuum hoses from VSV, located behind distributor. With ignition off, disconnect electrical connector from VSV. Using ohmmeter, check resistance between VSV terminals. Replace VSV if resistance is not 33-39 ohms. If resistance is okay, blow air into port "A" (to backpressure transducer). see scheme 48and see scheme 49. Air should pass through air filter and not through port "B" (to ported vacuum). Replace assembly if air passes through port "B".
2. Install electrical connector on VSV. Turn ignition on. Install jumper wire between terminals "A" and "C" of ALDL. (Scheme 147) ALDL is located under left side of dash (Rodeo 3.2L and Trooper).
3. Blow air into port "A". Air should pass from port "B". If air does not pass from port, check wiring between ECM and VSV. If wiring is okay, replace VSV.

EGR Valve

Using a vacuum pump, apply vacuum to EGR valve diaphragm. EGR valve diaphragm should hold vacuum. Ensure vacuum does not leak down and EGR valve diaphragm moves to a fully open position. Inspect EGR valve diaphragm for cracking. Check valve and seat for deformation and carbon deposits. Replace EGR valve if defective.

Thermal Vacuum Valve (TVV) (Amigo & Pickup 2.6L Federal; Rodeo 2.6L)

Disconnect TVV vacuum hoses. With engine coolant temperature less than 95°F (35°C), air should not pass through valve. With coolant temperature greater than 129°F (54°C), air should pass through valve. Replace TVV if defective. (Scheme 151)

CHART C-7 - EGR SYSTEM PICKUP 3.1L

ECM operates a solenoid in EGR control module to control vacuum to EGR valve. This solenoid is normally closed. ECM provides a ground to solenoid and solenoid opens, allowing vacuum to EGR valve.

ECM controls EGR based on following inputs

1. Engine coolant temperature is greater than 77°F (25°C).
2. TPS is off idle.
3. MAP sensor readings.

Note. Test numbers refer to numbers on diagnostic chart.

1. With ignition on and engine off, solenoid should not be energized and vacuum should not pass to EGR valve.
2. Grounding diagnostic terminal will energize solenoid, allowing vacuum to pass to EGR valve.
3. This test checks for plugged EGR passages. If passages are plugged, engine may have severe detonation on acceleration.
4. Solenoid is not energized in Park or Neutral. This test will determine if switch input is being received by ECM.

Scheme 154

Scheme 155

CHART C-7A - EGR SYSTEM RODEO 3.2L & TROOPER

ECM operates a Vacuum Switching Valve (VSV) to control vacuum to EGR valve. This solenoid is normally closed. ECM provides a ground to solenoid and VSV opens, allowing vacuum to EGR valve.

Engine control system operates within 2 block learn cells, a closed throttle cell and an open throttle cell. Open throttle cell is affected by EGR operation. When EGR system is operating correctly, block learn in both cells should be approximately the same. If EGR system is inoperative, block learn value at open throttle would increase, but block learn value at closed throttle would not change. This change or difference in block learn values is used to monitor EGR operation.

EVAPORATIVE EMISSION SYSTEM (EVAP)

Note. On Amigo 2.6L, Pickup 2.6L and Rodeo 2.6L, ensure evaporative system operating parameters are correct when testing EVAP system. (Scheme 156) Canister purge vacuum solenoid valve is also known as canister purge vacuum switching valve.

Canister Purge Vacuum Switching Valve (VSV) (Amigo, Pickup & Rodeo 2.6L)

1. Disconnect canister purge VSV harness connector, located on left fender panel, near canister. VSV harness connector wire colors are Black/White and Green/White. DO NOT confuse VSV connector with fuel pressure regulator connector.
2. Apply battery voltage to Blue wire terminal of VSV connector, and ground Black wire terminal. Ensure air does not flow freely between ports "Y" and "Z". Air should flow freely between ports "X" and "Y". (Scheme 157)
3. Disconnect battery voltage from VSV connector. Ensure air flows freely between ports "Y" and "Z". Air should not flow freely between ports "X" and "Y". If VSV does not perform as indicated, replace canister purge VSV.

Scheme 156

Scheme 157

Canister Purge Control Valve (Amigo, Pickup & Rodeo 2.6L)

1. With engine off, disconnect vacuum hose from lower port "A". (Scheme 158)and (Scheme 159). Connect a short section of hose to lower port "A", and blow air into it. Ensure air does not flow freely into charcoal canister.
2. Connect hand-held vacuum pump to lower port "A", and apply 15 in. Hg. Purge control valve should hold vacuum. If it does not hold vacuum, replace purge control valve. With vacuum holding at port "A", install second hand-held vacuum pump to purge control valve port. Gradually apply vacuum to purge control valve port. Purge control valve should open at 7.1-8.7 in. Hg. Replace purge control valve if it does not perform as indicated.
3. Start engine, and let idle. Disconnect vacuum hose from port "C". Ensure vacuum is not present at ports "B" and "D". If vacuum is present at idle, check for improperly routed vacuum hoses or defective purge control valve.

Scheme 158

Scheme 159

In-Tank Pressure Control Valve (Pickup 3.1L)

1. In-tank pressure control valve, located in fuel tank sending unit, is a combination roll-over, integral pressure and vacuum relief valve.
2. If vapor pressure in tank exceeds 1 in. Hg, valve opens and allows vapors to vent to canister. In-tank pressure control valve provides pressure relief to protect against pressure build-up in fuel tank and roll-over protection in an accident.

Thermostatic Vacuum Switch (TVS) (Pickup 3.1L)

TVS is installed in intake manifold coolant passage. TVS is closed until coolant temperature reaches 115°F (46°C), when it opens and purges vapor canister. (Scheme 160)

Scheme 160

PCV Valve

1. With engine running, remove PCV valve from rocker cover. Place thumb over end of valve to check for vacuum. If vacuum is present, go to step 3).
2. If no vacuum is present, remove PCV valve. If vacuum is present when valve is removed or engine dies, replace valve. If engine RPM changes little or does not change after removing valve from hose, replace vacuum hose between throttle body or intake manifold and PCV valve.
3. Turn ignition off. Remove PCV valve. Blow air into PCV valve from cylinder head side of valve. Ensure air flows through valve easily. DO NOT suck air through valve.
4. Blow air into intake manifold side of PCV valve. Ensure air does not flow through other side of valve. If valve does not function as indicated or valve does not rattle when shaken, replace PCV valve.

With engine off and air cleaner installed, TAC snorkel damper door should be open. When cold engine is first started, damper door should close to outside air. If door fails to operate, perform VACUUM MOTOR CHECK and TEMPERATURE SENSOR CHECK.

Vacuum Motor Check

Check all related vacuum hoses for kinks, breaks and plugs. With engine off, disconnect vacuum hose at TAC vacuum motor. Using hand-held vacuum pump, apply 7 in. Hg to motor. Damper door should close off intake (cold air) end of snorkel. If damper door does not close, check linkage and door for binding. If no problem is found, replace vacuum motor on air cleaner.

Temperature Sensor Check

1. With engine temperature less than 86°F (30°C), place a thermometer inside air cleaner as close to sensor as possible. Reinstall air cleaner cover. Start engine, and let idle.
2. Damper door should close immediately. If it does not, check vacuum hoses to sensor from throttle body and to vacuum motor from sensor. If vacuum hoses and vacuum motor are okay, replace sensor.
3. Observe when damper door opens snorkel passage. Remove air cleaner cover and note thermometer. Temperature should be approximately 131°F (55°C). If temperature is not as indicated, replace sensor.

MISCELLANEOUS CONTROLS

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

For diagnosis of A/C clutch control, see CHART C-10, A/C CLUTCH CONTROL DIAGNOSIS. (Scheme 152)and (Scheme 154).

Starter relay test procedure is same as fuel pump relay. See FUEL PUMP RELAY under FUEL DELIVERY .