Engine Controls - System/component Tests - Diesel Dodge Pickup R3500

INTRODUCTION

Note. Article applies only to 12-valve engine with mechanical fuel injection. Article does not apply to 24-valve engine with electronic fuel injection.

Before testing separate components or systems, perform procedures in appropriate BASIC TESTING article. Since many computer-controlled and monitored components set a diagnostic trouble code if they malfunction, also perform procedures in appropriate TESTS W/CODES article.

Note. Testing individual components does not isolate short or open circuits. 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 shorted or open wiring harness.

INTAKE MANIFOLD AIR HEATER SYSTEM

See INTAKE MANIFOLD AIR HEATER SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS.

INTERCOOLER

Cleaning and inspection procedures for intercooler is the only information available from manufacturer. See INTERCOOLER under AIR INDUCTION SYSTEMS in REMOVE/INSTALL/OVERHAUL article.

TURBOCHARGER

Note. Manufacturer does not recommend turbocharger disassembly. Turbocharger overhaul should be performed only by an authorized repair facility.

Turbocharger Boost Pressure

Turbocharger boost pressure testing information is not available from manufacturer.

TURBOCHARGER WASTEGATE

See CONTROL ROD ADJUSTMENT under TURBOCHARGER WASTE-GATE in ADJUSTMENTS article.

POWERTRAIN CONTROL MODULE (PCM)

The PCM is located on firewall at passenger's side rear corner of engine compartment. (Scheme 17) The PCM power and ground circuits may be checked by performing specified No Trouble Code (NTC) test. See TEST NTC-3A in appropriate TESTS W/CODES article.

Scheme 17

Battery Temperature Sensor

1. Battery temperature sensor is snapped into battery tray, below driver's side battery. Disconnect wiring harness at battery temperature sensor.
2. Using ohmmeter, check resistance between electrical terminals on battery temperature sensor. Resistance should be 9000-11,000 ohms at 75-80°F (25-27°C). Replace battery temperature sensor if resistance is not within specification.
3. If problem exists in battery temperature sensor or wiring circuit, a Diagnostic Trouble Code (DTC) will be stored in Powertrain Control Module (PCM). See appropriate TESTS W/CODES article.

Engine Coolant Temperature Sensor (Calif. Models With EGR)

1. Engine coolant temperature sensor is located on driver's side of engine, behind fuel filter/water separator, just below intake manifold. (Scheme 18)
2. Disconnect wiring harness electrical connector for engine coolant temperature sensor from engine wiring harness. Wiring harness electrical connector is located near top of fuel filter/water separator.
3. Using ohmmeter, check resistance between electrical terminals on wiring harness electrical connector for engine coolant temperature sensor. Replace engine coolant temperature sensor if resistance is not within specification in relation to engine coolant temperature. See ENGINE COOLANT TEMPERATURE SENSOR RESISTANCE table.
4. If problem exists in engine coolant temperature sensor or wiring circuit, a Diagnostic Trouble Code (DTC) will be stored in Powertrain Control Module (PCM). See appropriate TESTS W/CODES article.

ENGINE COOLANT TEMPERATURE SENSOR RESISTANCE

Scheme 18

Engine Speed Sensor

Engine speed sensor may also be referred to as Crankshaft Position (CKP) sensor. Engine speed sensor is located on front of timing gear cover, just above vibration damper. (Scheme 19) If problem exists in engine speed sensor, a Diagnostic Trouble Code (DTC) will be stored in Powertrain Control Module (PCM). See appropriate TESTS W/CODES article.

Scheme 19

Fuel Heater Temperature Sensor

See FUEL DELIVERY under FUEL SYSTEM.

Intake Manifold Air Temperature Sensor

1. Intake manifold air temperature sensor is located on top of intake manifold, behind intake manifold air heater. (Scheme 20)
2. Disconnect electrical connector from intake manifold air temperature sensor. Using ohmmeter, check resistance between electrical terminals on intake manifold air temperature sensor. Resistance should be within specification in relation to air temperature. See INTAKE MANIFOLD AIR TEMPERATURE SENSOR RESISTANCE table. Replace intake manifold air temperature sensor if resistance is not within specification.
3. To check wiring harness, check resistance on wires between intake manifold air temperature sensor and Powertrain Control Module (PCM). The PCM is located on firewall at right rear corner of engine compartment. (Scheme 17)
4. Using ohmmeter, check resistance on Black/Red wire between intake manifold air temperature sensor and terminal A15 (Black/Red wire) on Black 32-pin PCM connector. Check resistance on Black/Light Blue wire between intake manifold air temperature sensor and terminal A4 (Black/Light Blue wire) on Black 32-pin PCM connector. Resistance should be one ohm or less. Repair wiring if resistance is more than one ohm.
5. If problem exists in intake manifold air temperature sensor or wiring circuit, a Diagnostic Trouble Code (DTC) will be stored in Powertrain Control Module (PCM). See appropriate TESTS W/CODES article.

INTAKE MANIFOLD AIR TEMPERATURE SENSOR RESISTANCE

Scheme 20

Throttle Position Sensor (A/T Models & M/T Models With EGR)

For testing and adjustment of throttle position sensor, see THROTTLE POSITION SENSOR ADJUSTMENT under THROTTLE POSITION SENSOR in ADJUSTMENTS article.

Transmission Governor Pressure Sensor (A/T Models)

See TRANSMISSION under MISCELLANEOUS CONTROLS.

Transmission Speed Sensor (A/T Models)

See TRANSMISSION under MISCELLANEOUS CONTROLS.

Transmission Temperature Sensor (A/T Models)

See TRANSMISSION under MISCELLANEOUS CONTROLS.

Water-In-Fuel (WIF) Sensor

Water-in-fuel sensor is located in bottom of fuel filter/water separator. (Scheme 26) Testing information is not available from manufacturer.

A/C Switch

Testing information is not available from manufacturer.

Brake Switch

1. Remove lower panel for access to brake switch. Brake switch is located on bracket, near top of brake pedal.
2. Disconnect electrical connector from brake switch. Pull plunger on brake switch fully outward. (Scheme 21)
3. Using ohmmeter, check for continuity between terminals No. 5 and 6 on brake switch. (Scheme 21) Continuity should exist. If continuity exists, go to next step. If continuity does not exist, replace brake switch.
4. Push plunger on brake switch fully inward. Using ohmmeter, check for continuity between terminals No. 1 and 2, and 3 and 4 on brake switch. (Scheme 21) Continuity should exist. If continuity does not exist, replace brake switch.

Scheme 21

Park/Neutral Switch (A/T Models)

See TRANSMISSION under MISCELLANEOUS CONTROLS.

Transmission Overdrive Switch (A/T Models)

See TRANSMISSION under MISCELLANEOUS CONTROLS.

A/C Clutch Relay

A/C clutch relay may also be referred to as A/C compressor clutch relay. A/C clutch relay is located in power distribution center at driver's side front corner of engine compartment, near battery. If problem exists in A/C clutch relay or wiring circuit, a Diagnostic Trouble Code (DTC) will be stored in Powertrain Control Module (PCM). See appropriate TESTS W/CODES article.

Auto Shutdown (ASD) Relay

ASD relay is located in power distribution center at driver's side front corner of engine compartment, near battery. If problem exists in ASD relay or wiring circuit, a Diagnostic Trouble Code (DTC) will be stored in Powertrain Control Module (PCM). See appropriate TESTS W/CODES article.

Fuel Heater Relay & Fuel Shutdown Solenoid Relay

1. Fuel heater relay and fuel shutdown solenoid relay are located in engine compartment, next to brake master cylinder. (Scheme 22) Remove relay and note terminal identification on relay. (Scheme 23)
2. Using ohmmeter, check resistance between terminals No. 85 and 86 on relay. Resistance should be 70-80 ohms. If resistance is within specification, go to next step. If resistance is not within specification, replace relay.
3. Using ohmmeter, ensure continuity exists between terminals No. 30 and 87A on relay. If continuity exists, go to next step. If no continuity exists, replace relay.
4. Using ohmmeter, ensure no continuity exists between terminals No. 30 and 87 on relay. If no continuity exists, go to next step. If continuity exists, replace relay.
5. Using jumper wires, connect terminal No. 85 to negative side of 12-volt power source and terminal No. 86 to positive side of 12-volt power source. CAUTION: DO NOT allow ohmmeter leads to contact terminals No. 85 and 86 on relay when checking resistance.
6. Using ohmmeter, ensure no continuity now exists between terminals No. 30 and 87A on relay. If no continuity exists, go to next step. If continuity exists, replace relay.
7. Using ohmmeter, ensure continuity now exists between terminals No. 30 and 87 on relay. If continuity exists, disconnect jumper wires from relay. If no continuity exists, replace relay.

Note. For additional information on checking wiring circuit for fuel heater relay, see NO TROUBLE CODE (NTC-29A) TEST and NO START (NS-14A) TEST in appropriate TESTS W/CODES article. For additional information on checking wiring circuit for fuel shutdown solenoid relay, see NO START (NS-15A) TEST in appropriate TESTS W/CODES article.

Scheme 22

Scheme 23

Intake Manifold Air Heater Relays

1. Intake manifold air heater relays may also be referred to as intake air heater relays. Intake manifold air heater relays are mounted on inner wheelwell, below driver's side battery. (Scheme 24)
2. Disconnect negative battery cables. Note location of wiring on intake manifold air heater relays for reassembly reference. Disconnect all electrical connectors and cables from intake manifold air heater relays.
3. Connect ohmmeter between large terminals on intake manifold air heater relay to check for continuity. Using jumper wires, momentarily apply battery voltage to relay trigger wire terminals (small wire terminals) at base of intake manifold air heater relay. (Scheme 24) Polarity is not important.
4. Intake manifold air heater relay should click and ohmmeter should indicate continuity between large terminals when battery voltage is applied to relay trigger wire terminals. If intake manifold air heater relay operation is not as specified, replace intake manifold air heater relay with bracket. Test remaining intake manifold air heater relay. Remove ohmmeter. Reconnect all electrical connectors and negative battery cables.

Note. For additional information on checking wiring circuit for intake manifold air heater relay, see NO TROUBLE CODE (NTC-30A and NTC-31A) TESTS in appropriate TESTS W/CODES article.

Scheme 24

Transmission Relay (A/T Models)

Transmission relay may be referred to as transmission control relay or transmission 12-volt supply relay. Transmission relay is located in power distribution center at driver's side front corner of engine compartment, near battery. If problem exists in transmission relay or wiring circuit, a Diagnostic Trouble Code (DTC) will be stored in Powertrain Control Module (PCM). See appropriate TESTS W/CODES article.

EGR Valve Vacuum Regulator Solenoid (Calif. Models Only)

See EXHAUST GAS RECIRCULATION (EGR) SYSTEM (CALIF. MODELS ONLY) under EMISSION SYSTEMS & SUB-SYSTEMS.

Fuel Shutdown Solenoid (Preliminary Inspection)

1. Ensure ignition switch is in OFF position. Ensure lever pin on fuel shutdown solenoid is extended downward and pump lever is in SHUTDOWN position. (Scheme 25)
2. Turn ignition switch to START position while noting operation of lever pin and pump lever. Lever pin and pump lever should move upward to RUN position. (Scheme 25) Release ignition switch from START position to ON position. Ensure lever pin and pump lever remain in RUN position.
3. If fuel shutdown solenoid operates as specified, fuel shutdown solenoid and wiring are okay. If fuel shutdown solenoid does not operate as specified, go to appropriate procedure as follows, depending on operation of solenoid and lever pin.

Fuel Shutdown Solenoid Does Not Operate (Lever Pin Does Not Move Upward At All)

1. Disconnect fuel shutdown solenoid connector from wiring harness. (Scheme 20) While holding ignition switch in START position, use voltmeter to check voltage at Red/Violet wire terminal on wiring harness side of fuel shutdown solenoid connector. Red/Violet wire goes to fuel shutdown solenoid relay. Battery voltage should exist.
2. If battery voltage does not exist, go to next step. If battery voltage exists, replace fuel shutdown solenoid. See FUEL SHUTDOWN SOLENOID under FUEL SYSTEM in REMOVE/INSTALL/OVERHAUL article.
3. Check fuel shutdown solenoid relay. See RELAYS under RELAYS & SOLENOIDS. If fuel shutdown solenoid relay is okay, go to next step. If fuel shutdown solenoid relay is defective, replace fuel shutdown solenoid relay and recheck operation.
4. If fuel shutdown solenoid relay is okay, check for open circuit on Red/Violet wire between fuel shutdown solenoid relay and fuel shutdown solenoid, and for open wiring circuit from starter and fuse No. 9 (50-amp) in power distribution center to fuel shutdown solenoid relay. See appropriate wiring diagram in WIRING DIAGRAMS article. Power distribution center is located at driver's side front corner of engine compartment, near fenderwell.

Fuel Shutdown Solenoid Operates Only With Ignition Switch In START Position (Lever Pin Moves Upward But Does Not Stay Up)

1. Disconnect fuel shutdown solenoid connector from wiring harness. (Scheme 20) Turn ignition switch to ON position.
2. Using voltmeter, check voltage at Light Green/Black wire terminal on wiring harness side of fuel shutdown solenoid connector. This is the wire from ignition switch and fuse No. 9 (10-amp) to fuel shutdown solenoid. Fuse No. 9 is located in junction block on end of instrument panel, at driver's door opening.
3. If battery voltage exists, replace fuel shutdown solenoid. See FUEL SHUTDOWN SOLENOID under FUEL SYSTEM in REMOVE/INSTALL/OVERHAUL article. If battery voltage does not exist, repair open circuit on Light Green/Black wire between ignition switch and fuel shutdown solenoid. See appropriate wiring diagram in WIRING DIAGRAMS article.

Transmission Overdrive Solenoid (A/T Models)

See TRANSMISSION under MISCELLANEOUS CONTROLS.

Transmission Torque Converter Clutch Solenoid (A/T Models)

See TRANSMISSION under MISCELLANEOUS CONTROLS.

Scheme 25

Scheme 26

Fuel Filter/Water Separator

1. A restricted fuel filter/water separator may cause engine starting problems, prevent engine from accelerating, low power or White exhaust smoke.
2. When ignition is first turned on, WATER-IN-FUEL (WIF) warning light should come on for 2 seconds to perform bulb and wiring circuit test and then go off. WATER-IN-FUEL (WIF) warning light is located on instrument panel, just below tachometer.
3. If WATER-IN-FUEL (WIF) warning light stays on, water should be drained from fuel filter/water separator. To drain water from fuel filter/water separator, ensure engine is not running. Place drain pan below drain tube at fuel filter/water separator. (Scheme 26)
4. Rotate handle on drain valve forward, toward front of vehicle to DRAIN position. Drain valve is located near top of fuel filter/water separator. (Scheme 26)
5. If no water exists and a clean flow of diesel fuel exists, rotate handle on drain valve back to CLOSE position. Go to next step. If water exists, allow water to drain until clean flow of diesel fuel exists. Rotate handle on drain valve back to CLOSE position. Go to next step.
6. Verify fuel filter/water separator has been serviced according to proper service schedule. See SERVICE INTERVALS & SPECIFICATIONS under QUICK-SERVICE in SPECIFICATIONS article. Ensure pre-filter was cleaned when fuel filter/water separator was serviced. Pre-filter is located at bottom of fuel heater on driver's side of engine. (Scheme 26) No other testing information is available from manufacturer.

Fuel Heater

1. Malfunctioning fuel heater may cause excessive wax build-up in fuel filter/water separator during cold ambient temperatures. Wax build-up may cause hard starting, prevent engine from accelerating, low power, or Blue or White smoke.
2. Disconnect electrical connector at fuel heater. Fuel heater is located between pre-filter and fuel transfer pump. (Scheme 26) Using ohmmeter, check resistance between electrical terminals on fuel heater.
3. Resistance should be about one ohm when fuel is cold, and about 1000 ohms when fuel is warm. Replace fuel heater if resistance is not within specification.

Note. Fuel heater receives battery voltage from fuel heater relay. Fuel heater relay is located in engine compartment, next to brake master cylinder. (Scheme 22) For testing of fuel heater relay, see RELAYS under RELAYS & SOLENOIDS. Consult wiring diagram for wiring circuit testing. See appropriate wiring diagram in WIRING DIAGRAMS article.

1. Disconnect electrical connector at fuel heater. (Scheme 26) Fuel heater temperature sensor is located on fuel heater. (Scheme 26)
2. Using ohmmeter, check for continuity between electrical terminals for fuel heater temperature sensor. If fuel temperature is greater than 80°F (26.7°C), no continuity should exist. If fuel temperature is less than 40°F (4.4°C), continuity should exist. Replace fuel heater temperature sensor if continuity is not as specified.

Note. A defective fuel transfer pump may cause low power, hard starting and White smoke. Check fuel transfer pump output pressure, and then fuel transfer pump output volume. Low fuel transfer pump output pressure may also be caused by worn eccentric on engine camshaft.

Fuel Transfer Pump Preliminary Inspection

1. Check for restricted or leaking fuel supply line to fuel transfer pump or fuel return line located on driver's side of engine. (Scheme 26) Repair fuel supply line or fuel return line if restricted or leaking.
2. Check for fuel leaking from weep hole on housing of fuel transfer pump. Replace fuel transfer pump if fuel is leaking from weep hole. Check fuel transfer pump output pressure.

Fuel Transfer Pump Output Pressure

1. Place drain pan below fuel injection pump. Remove banjo bolt and gaskets, and disconnect fuel supply line from side of fuel injection pump. (Scheme 27)
2. Using Adapter (6976) and gaskets, reconnect fuel supply line on side of fuel injection pump. (Scheme 27) Install a 0-100 psi fuel pressure gauge on adapter.
3. Start engine and warm engine to normal operating temperature. Record output pressure with engine idling and then at 2500 RPM with no load. Output pressure should be 17-22 psi (117-152 kPa) at idle and 25-30 psi (172-207 kPa) at 2500 RPM with no load.
4. If output pressure is within specification, go to step 11). If output pressure exceeds specification, go to next step. If output pressure is less than specification, go to step 6).
5. High output pressure indicates a restriction. Ensure overflow valve is installed on fuel return line on fuel injection, and not on fuel supply line. Overflow valve is used to secure fuel return line on fuel injection pump. (Scheme 28) If overflow valve is installed in improper fuel line, reinstall in correct location and recheck output pressure. If overflow valve is installed in correct location, check for fuel line restrictions.
6. Check for dirty or restricted fuel filter/water separator and pre-filter. Fuel filter/water separator and pre-filter are located on driver's side of engine. (Scheme 26) Pre-filter is located at bottom of fuel heater. (Scheme 26)
7. Change dirty or restricted fuel filter/water separator or pre-filter as necessary and recheck output pressure. If output pressure is now within specification, go to step 11). If output pressure is still less than specification, overflow valve on fuel injection pump may be defective. Overflow valve is used to secure fuel return line on fuel injection pump. (Scheme 28) Go to next step.
8. To determine if overflow valve is defective, disconnect fuel return line at rear of engine. (Scheme 26) Install Rubber Adapter Hose (6539) between fuel return line on engine and fuel return line going back to fuel tank. CAUTION: Rubber adapter hose must be installed when pinching fuel return line closed. DO NOT attempt to pinch fuel return line from engine to fuel tank closed. Fuel return line is rubber on the outside, but the inside is not rubber and fuel return line will be damaged if it is pinched closed.
9. Carefully pinch fuel return line closed and note output pressure. If output pressure is still less than specification, go to next step. If output pressure is now within specification, ensure overflow valve is installed on fuel return line on fuel injection, and not on fuel supply line. (Scheme 28) If overflow valve is installed in correct location, replace overflow valve. If overflow valve is installed in improper fuel line, reinstall in correct location and recheck output pressure.
10. If output pressure is still less than specified with fuel return line pinched closed, ensure fuel filter/water separator or pre-filter are in good condition. If fuel filter/water separator and pre-filter are okay, replace transfer pump.
11. Shut engine off. Remove test equipment. Reinstall fuel supply line on fuel injection pump. Install and tighten fuel supply banjo bolt to 18 ft. lbs. (24 N.m). Check fuel transfer pump output volume. See FUEL TRANSFER PUMP OUTPUT VOLUME.

Scheme 27

Scheme 28

Fuel Transfer Pump Output Volume

1. Disconnect fuel shutdown solenoid connector. (Scheme 20) This is done to prevent engine from starting, as engine must be cranking to check fuel transfer pump output volume. Connect hand-held Tachometer (3377462) to engine.
2. Remove fuel drain line-to-cylinder head clamp bolt near cylinder No. 5 rocker lever cover. This is done to prevent damage to fuel drain line when disconnecting fuel drain line from fuel filter/water separator. Remove banjo bolt and disconnect fuel drain line from fuel inlet line at top of fuel filter/water separator. (Scheme 29)
3. Using Adapter (6836), secure fuel inlet line to top of fuel filter/water separator. (Scheme 29) Connect rubber hose on adapter. Place remaining end of rubber hose in graduated container which measures ounces.
4. Crank engine for 30 seconds while noting engine cranking speed RPM. DO NOT crank engine for more than 30 seconds or starter may be damaged. Note amount of fuel volume obtained.
5. To determine fuel transfer pump output volume specification, use engine cranking speed RPM and fuel volume. (Scheme 30)
6. If fuel transfer pump output volume is less than specified, condition may be caused by a restricted fuel supply inlet line, restricted pre-filter or defective transfer pump. Remove test equipment. Reinstall fuel drain line and fuel shutdown solenoid connector.

Scheme 29

Scheme 30

Overflow Valve

Overflow valve is used to secure fuel return line on fuel injection pump. (Scheme 28) A sticking check valve in overflow valve may result in low power. Overflow valve operation may be checked when testing fuel transfer pump. See FUEL TRANSFER PUMP OUTPUT PRESSURE and FUEL TRANSFER PUMP OUTPUT VOLUME under FUEL DELIVERY.

Fuel Injection Pump

Ensure fuel transfer pump output pressure and volume are within specification before condemning fuel injection pump. See FUEL TRANSFER PUMP OUTPUT PRESSURE and FUEL TRANSFER PUMP OUTPUT VOLUME under FUEL DELIVERY. Check for proper fuel injection pump timing before condemning fuel injection pump. See CHECKING FUEL INJECTION PUMP TIMING under FUEL INJECTION PUMP TIMING in ADJUSTMENTS article. Fuel injection pump testing must only be done by an authorized repair facility.

FUEL CONTROL

Note. A leaking fuel injector or high-pressure fuel line may cause a rough idle, Black smoke, poor engine performance, poor fuel economy and fuel knock. Following procedure is for determining if fuel injector is defective.

Fuel Injector

1. Since a leaking high-pressure fuel line may cause the same symptoms, check for leaking high-pressure fuel line before checking fuel injector. To check for a leaking high-pressure fuel line, start engine and allow engine to idle.
2. Inspect high-pressure fuel lines and connections for signs of fuel leakage by placing cardboard over high-pressure fuel line and connection. Note if leak is being detected by fuel being sprayed onto cardboard. If leak exists, repair leak by tightening high-pressure fuel line nut to 18 ft. lbs. (24 N.m) or replacing high-pressure fuel line as necessary. If high-pressure fuel line is replaced, bleed air from fuel system. See FUEL LINE BLEEDING under FUEL SYSTEM in REMOVE/INSTALL/OVERHAUL article.
3. To check for defective fuel injector, start engine and engine allow to idle. Loosen high-pressure fuel line nut at fuel injector and listen for a decrease in engine speed. Tighten high-pressure fuel line nut to 18 ft. lbs. (24 N.m).
4. If fuel injector is operating properly, engine idle speed should decrease when high-pressure fuel line nut is loosened. Repeat procedure on each fuel injector.
5. If engine idle speed does not decrease, fuel injector is defective and should be removed and tested with a diesel fuel injector tester. Replace fuel injector if fuel injector opening (pop) pressure is not 3394-3887 psi (239-273 kg/cm 2 ).

Fuel Shutdown Solenoid

See SOLENOIDS under RELAYS & SOLENOIDS.

EGR System Test

1. Check for Diagnostic Trouble Codes (DTCs) pertaining to EGR system. See appropriate TESTS W/CODES article. If no DTCs pertaining to EGR system exist, go to next step. If any DTCs for EGR system exist, ensure repair procedures for DTC are performed and then proceed to next step. NOTE: EGR valve operation cannot be checked by applying vacuum to EGR valve with engine idling, as opening of EGR valve will not affect engine idle speed.
2. Using scan tool, follow scan tool manufacturer's instructions and check operation of EGR valve vacuum regulator solenoid and electrical circuit. If EGR valve vacuum regulator solenoid and electrical circuit are operating properly, go to next step. If EGR valve vacuum regulator solenoid and electrical circuit is not operating properly, repair system as necessary and go to next step.
3. Start engine and allow engine to idle. Ensure vacuum exists on inlet side of EGR valve vacuum regulator solenoid. EGR valve vacuum regulator solenoid is located on driver's side of engine, just in front of EGR valve. (Scheme 31)
4. If vacuum exists at inlet side of EGR valve vacuum regulator solenoid, go to next step. If vacuum does not exist at inlet side of EGR valve vacuum regulator solenoid, check vacuum pump operation. See VACUUM PUMP OPERATION.
5. Check operation of EGR valve. See EGR VALVE. If EGR valve operates properly, check operation of EGR valve one-way check valve. See EGR VALVE ONE-WAY CHECK VALVE.

Note. For additional testing information of EGR system, see NO TROUBLE CODE (NTC-18A) TEST in appropriate TESTS W/CODES article.

Scheme 31

EGR Valve

1. Remove EGR valve from intake manifold and EGR tube. (Scheme 31)
2. Inspect EGR valve for excessive carbon deposits on head of poppet valve at base opening at end of EGR valve. (Scheme 32) Using flashlight, apply light at poppet valve opening and seat area on EGR valve. Light should not pass through poppet valve opening and seat area.
3. If no excessive carbon deposits exist and light does not pass through poppet valve opening and seat area, go to next step. If excessive carbon deposits exist or light passes through poppet valve opening and seat area, replace EGR valve. DO NOT attempt to clean poppet valve and seat area in EGR valve.
4. To check EGR valve operation, use vacuum pump to slowly apply 10 in. Hg of vacuum to EGR valve and note operation of poppet valve. (Scheme 32)
5. If poppet valve starts to open when 10 in. Hg of vacuum is applied and vacuum holds steady, go to next step. If poppet valve does not start to open when 10 in. Hg of vacuum is applied or vacuum does not hold steady, replace EGR valve.
6. Continue to increase vacuum supply to 20 in. Hg of vacuum. Poppet valve should be fully open at approximately 20 in. Hg of vacuum and vacuum should hold steady.
7. If poppet valve is fully open with 20 in. Hg of vacuum applied and vacuum holds steady, go to next step. If poppet valve does not fully open with 20 in. Hg of vacuum applied or vacuum does not hold steady, replace EGR valve.
8. EGR valve is operating properly. If EGR valve is operating properly, but EGR system does not operate, check for restricted passages in EGR tube, exhaust manifold and intake manifold due to excessive carbon deposits. EGR tube fits between intake manifold and exhaust manifold. (Scheme 31)

Scheme 32

EGR Valve Vacuum Regulator Solenoid

1. EGR valve vacuum regulator solenoid is located on driver's side of engine, just in front of EGR valve. (Scheme 31) EGR valve vacuum regulator solenoid controls vacuum to EGR valve and is controlled by Powertrain Control Module (PCM).
2. For checking operation of EGR valve vacuum regulator solenoid and electrical circuit, use scan tool and follow scan tool manufacturer's instructions. For additional testing information of EGR system, see NO TROUBLE CODE (NTC-18A) TEST in appropriate TESTS W/CODES article. If EGR valve vacuum regulator solenoid and electrical circuit is not operating properly, repair system as necessary and check remaining components in system to ensure proper system operation.

EGR Valve One-Way Check Valve

1. EGR valve one-way check valve is located between EGR valve and EGR valve vacuum regulator solenoid on driver's side of engine. (Scheme 31)
2. EGR valve one-way check valve allows vacuum to be quickly released from EGR valve. If EGR valve one-way check valve is defective, EGR valve may remain open as vacuum is not released from EGR valve, or EGR valve may not operate, as vacuum supply to EGR valve is being released.
3. Using "T" fitting, install vacuum gauge in vacuum hose between EGR valve and EGR valve vacuum regulator solenoid. EGR valve vacuum regulator solenoid is located on driver's side of engine, just in front of EGR valve. (Scheme 31)
4. Start engine and warm engine to normal operating temperature to allow EGR system operation. Road test vehicle at a steady speed and observe vacuum reading.
5. High vacuum should be obtained when driving at a steady speed. Quickly open throttle and note vacuum reading. Vacuum should rapidly decrease to no vacuum when throttle is opened.
6. If vacuum does not quickly decrease to no vacuum, go to next step. If vacuum quickly decreases to no vacuum, EGR valve one-way check valve is operating properly. Remove vacuum gauge and reconnect vacuum hose.
7. Using scan tool, follow scan tool manufacturer's instructions and check operation of EGR valve vacuum regulator solenoid and electrical circuit. If EGR valve vacuum regulator solenoid and electrical circuit are operating properly, but vacuum does not decrease to no vacuum, go to next step. If EGR valve vacuum regulator solenoid and electrical circuit are not operating properly, repair system as necessary.
8. Remove vacuum gauge. Disconnect vacuum hoses from both vacuum hose fittings on EGR valve one-way check valve. Install vacuum pump on solenoid side of EGR valve one-way check valve. (Scheme 33) This is the side that goes to EGR valve vacuum regulator solenoid. NOTE: Ensure at least 20 in. Hg of vacuum is applied on EGR valve one-way check valve when testing.
9. Plug EGR valve side of EGR valve one-way check valve. Apply at least 20 in. Hg of vacuum to EGR valve one-way check valve. Vacuum should hold steady and no vacuum leakage should exist. If vacuum holds steady, go to next step. If vacuum does not hold steady, replace EGR valve one-way check valve.
10. Release vacuum. Disconnect vacuum pump from solenoid side of EGR valve one-way check valve. Install vacuum pump on EGR valve side of EGR valve one-way check valve. (Scheme 33)
11. Plug solenoid side of EGR valve one-way check valve. Attempt to apply vacuum to EGR valve one-way check valve. No vacuum should be obtained. If vacuum cannot be obtained, EGR valve one-way check valve is operating properly. If vacuum can be obtained, replace EGR valve one-way check valve. Remove vacuum pump and reconnect all vacuum hoses on EGR valve one-way check valve.

Scheme 33

Vacuum Pump Operation

1. The gear-driven vacuum pump provides vacuum source for operation of EGR system, brake system and various vacuum-controlled devices. Vacuum pump is located between power steering pump and gear housing on driver's side of engine. (Scheme 26)
2. Vacuum pump should have a vacuum output of 8.5-25 in. Hg depending engine speed. No other testing information is available from manufacturer.

Intake Manifold Air Heater Preheat/Postheat Cycle

1. Air temperature at intake manifold must be less than 59°F (15°C). Turn ignition on. DO NOT start engine.
2. The WAIT-TO-START light on instrument panel should come on. WAIT-TO-START light is located on instrument panel, just below speedometer. A click should be heard from at intake manifold air heater relays, indicating preheat cycle has begun. Intake manifold air heater relays are mounted on inner wheelwell, below driver's side battery. (Scheme 24) NOTE: If starter is engaged before preheat cycle is complete, Powertrain Control Module (PCM) will stop preheat cycle.
3. Remove rubber cable terminal shields from cable connections on intake manifold air heater. Intake manifold air heater is located between air inlet housing and intake manifold cover. (Scheme 34)
4. Using voltmeter, check for voltage at both terminals on intake manifold air heater. Battery voltage should exist at both terminals for 10-30 seconds, depending on intake air temperature. See HEAT CYCLE SPECIFICATIONS table. HEAT CYCLE SPECIFICATIONS Intake Air Temperature Preheat Cycle With Ignition On & Engine Off Postheat Cycle With Ignition On & Engine On Greater Than 59°F (15°C) 0.0 Seconds No 15°F (-10°C) To 59°F (15°C) 10.0 Seconds Yes 0°F (-18°C) To 15°F (-10°C) 15.0 Seconds Yes Less Than 0°F (-18°C) 30.0 Seconds Yes
5. If voltage exists as specified, check intake manifold air heater. If voltage does not exist as specified, check intake manifold air heater relays.

Intake Manifold Air Heater

1. Disconnect negative battery cables. Remove rubber cable terminal shields from cable connections at intake manifold air heater. Intake manifold air heater is located between air inlet housing and intake manifold cover. (Scheme 34) DO NOT disconnect cables from intake manifold air heater.
2. Using ohmmeter, check resistance between ground and each cable connection. DO NOT use mounting stud for cable on intake manifold air heater when checking resistance. Resistance should be zero ohms.
3. If any resistance exists, check for corroded or dirty electrical connections. Clean and repair cable connections as necessary. Recheck resistance. If resistance still exists, go to next step.
4. Disconnect cable connections from intake manifold air heater. Isolate cables to prevent cables from contacting other components.
5. Using ohmmeter, check resistance between ground and each cable terminal on intake manifold air heater. Resistance should be zero ohms. If any resistance exists, replace intake manifold air heater with intake manifold cover. Reinstall cable connections and negative battery cables.

Intake Manifold Air Heater Relay

See RELAYS under RELAYS & SOLENOIDS.

See SENSORS under ENGINE SENSORS & SWITCHES.

Scheme 34

MISCELLANEOUS CONTROLS

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

Park/neutral switch is mounted on transmission case, near shift lever and contains a 3-pin connector. If problem exists in park/neutral switch or wiring circuit, a Diagnostic Trouble Code (DTC) will be stored in Powertrain Control Module (PCM). See appropriate TESTS W/CODES article.

Transmission governor pressure sensor is located on transmission valve body. If problem exists in transmission governor pressure sensor or wiring circuit, a Diagnostic Trouble Code (DTC) will be stored in Powertrain Control Module (PCM). See appropriate TESTS W/CODES article.

Transmission overdrive solenoid may also be referred to as overdrive solenoid or 3-4 solenoid. Transmission overdrive solenoid is located transmission valve body. If problem exists in transmission overdrive solenoid or wiring circuit, a Diagnostic Trouble Code (DTC) will be stored in Powertrain Control Module (PCM). See appropriate TESTS W/CODES article.

Transmission overdrive switch may be referred to as overdrive/override switch, OD switch or overdrive off switch. Transmission overdrive switch is located on end of gearshift lever. If problem exists in transmission overdrive switch or wiring circuit, a Diagnostic Trouble Code (DTC) will be stored in Powertrain Control Module (PCM). See appropriate TESTS W/CODES article.

See RELAYS under RELAYS & SOLENOIDS.

Transmission speed sensor may also be referred to as transmission output shaft speed sensor. Transmission speed sensor is located on overdrive case at rear of transmission. Transmission speed sensor contains a 2-pin connector with a Dark Blue/Black wire and a Light Green/Black wire. If problem exists in transmission speed sensor or wiring circuit, a Diagnostic Trouble Code (DTC) will be stored in Powertrain Control Module (PCM). See appropriate TESTS W/CODES article.

Transmission temperature sensor is incorporated into governor pressure sensor on transmission valve body. If problem exists in transmission temperature sensor or wiring circuit, a Diagnostic Trouble Code (DTC) will be stored in Powertrain Control Module (PCM). See appropriate TESTS W/CODES article.

The transmission Torque Converter Clutch (TCC) solenoid is located on transmission valve body. If problem exists in TCC solenoid or wiring circuit, a Diagnostic Trouble Code (DTC) will be stored in Powertrain Control Module (PCM). See appropriate TESTS W/CODES article.