Engine Controls - System & Component Testing: Other Land Rover Discovery II

Ground Circuits (Discovery)

1. Using a backprobe set, check for continuity in Black wires between ground connection and ECM Black 18-pin connector terminals No. 5, 9 and 10, individually. (Scheme 23) See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000). If continuity exists, go to next step. If continuity does not exist, repair open in suspect Black wire.
2. Start engine and allow to idle. Using a backprobe set, measure voltage between ground and ECM Black 18-pin connector terminals No. 5, 9 and 10. Voltage should be less than one volt. If voltage is greater than one volt, check for an open, corrosion or loose ground connection. See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000).

Power Circuits (Discovery)

Turn ignition on. Using a backprobe set, measure voltage between ground and ECM Black 18-pin connector terminal No. 8 (White/Green wire). See WIRING DIAGRAMS . If battery voltage does not exist, check fuse No. 3 (20-amp), located in satellite fuse box No. 1. If fuse is okay, check for an open in suspect circuit between fuse box and ECM. If fuse is not okay, repair short in suspect circuit and replace fuse. See WIRING DIAGRAMS .

Scheme 23

Ground Circuits (Discovery Series II & Range Rover)

1. Using a backprobe set, check for continuity in Black wires between ground and ECM Black 9-pin connector C0634 terminals No. 4, 5, and 6, Black 52-pin connector C0636 terminal No. 17 and Gray 9-pin connector C0638 terminal No. 5, individually. (Scheme 24)and (Scheme 25). See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000). On Discovery Series II, ground connection is located at right rear side of engine compartment. On Range Rover, ground connection is located at right side of engine compartment, near the horn. If continuity exists, go to next step. If continuity does not exist, repair open in suspect Black wire.
2. Start engine and allow to idle. Using a backprobe set, measure voltage between ground and ECM Black 9-pin connector C0634 terminals No. 4, 5, and 6, Black 52-pin connector C0636 terminal No. 17 and Gray 9-pin connector C0638 terminal No. 5, individually. Voltage should be less than one volt. If voltage is greater than one volt, check for an open, corrosion or loose ground connection. See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000).

Power Circuits (Discovery Series II)

1. Turn ignition off. Using a backprobe set, check for voltage between ground and ECM Black 9-pin connector C0634 terminal No. 7 (Purple/Yellow wire). If battery voltage is present, go to next step. If battery voltage is not present, check for open or short in Purple/Yellow wire between ECM and fuse No. 12 (20-amp) located in engine compartment fuse/relay box. (Scheme 24)and (Scheme 25). See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000). Perform repairs as necessary.
2. Turn ignition off. Using a backprobe set, measure voltage between ground and ECM Black 24-pin connector C0635 terminal No. 23 (Blue/Red wire). See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000). If battery voltage does not exist, ensure inertia switch is closed. If necessary, reset inertia switch and recheck for voltage. If inertia switch is closed, check circuit between ECM, main relay, inertia switch and fuse No. 13 (15-amp), located in engine compartment fuse/relay box. Perform repairs as necessary.

Power Circuits (Range Rover)

Turn ignition off. Using a backprobe set, check for voltage between ground and ECM Black 9-pin connector C0634 terminal No. 7 (Purple/Yellow wire). If battery voltage is present, go to next step. (Scheme 24)and (Scheme 25). See WIRING DIAGRAMS. If battery voltage is not present, check for open or short in Purple/Yellow wire between ECM and fuse No. 44 (30-amp) located in engine compartment fuse/relay box. Perform repairs as necessary.

Scheme 24

Scheme 25

CAMSHAFT POSITION (CMP) SENSOR & CRANKSHAFT POSITION (CKP) SENSOR SYNCHRONIZATION

1. CKP sensor is located on the left side of flywheel housing. CMP sensor is located on left front of engine.
2. Compare CKP sensor wave pattern with known-good pattern. Check wave pattern for bent teeth on reluctor ring and regularity. See DTC P0335 & P0336: CRANKSHAFT POSITION (CKP) SENSOR MALFUNCTION testing in appropriate SELF-DIAGNOSTICS article. If wave pattern is okay, go to next step. If CKP wave pattern is okay and engine misfire DTCs are set, see DTC P0300-P0308: MISFIRE DETECTED IN ONE OR MORE CYLINDERS testing in appropriate SELF-DIAGNOSTICS article. If wave pattern is not okay, go to «CRANKSHAFT POSITION (CKP) SENSOR»(ref-3175-S30118560272000041800000) .
3. Compare CMP sensor wave pattern with known-good wave pattern. See DTC P0340: CAMSHAFT POSITION (CMP) SENSOR MALFUNCTION in appropriate SELF-DIAGNOSTICS article. If wave pattern is okay, go to next step. If wave pattern is not okay, go to «CRANKSHAFT POSITION (CKP) SENSOR»(ref-3175-S30118560272000041800000) .
4. Compare synchronization of CKP sensor and CMP sensor wave patterns with known-good patterns. See DTC P0340: CAMSHAFT POSITION (CMP) SENSOR MALFUNCTION in appropriate SELF-DIAGNOSTICS article. If wave patterns are synchronized, both sensors are okay. If wave patterns are not synchronized, go to «CRANKSHAFT POSITION (CKP) SENSOR»(ref-3175-S30118560272000041800000) .

CAMSHAFT POSITION (CMP) SENSOR CIRCUIT

Note. It is physically possible to interchange the camshaft sprocket installed on vehicles equipped with GEMS ignition system and vehicles equipped with Bosch Motronic 5.2.1 ignition system. However, because the GEMS and Motronic systems are incompatible, an incorrect camshaft signal will be received by the ECM and DTC P0340 will set.

1. Check for CMP sensor output wave pattern. If there is no sensor output wave pattern, go to step 4 . If there is an output wave pattern, go to next step.
2. Compare wave pattern with known-good wave pattern. See DTC P0340: CAMSHAFT POSITION (CMP) SENSOR MALFUNCTION in appropriate SELF-DIAGNOSTICS article. If wave pattern is okay, go to next step. If wave pattern is not okay, ensure correct cam reluctor ring and cam shaft are installed in engine. It is possible for an incorrect camshaft to be installed in engine. If camshaft and reluctor ring are correct, ensure CMP sensor is correctly installed. Repair as necessary and recheck wave pattern.
3. Compare synchronization of CKP sensor and CMP sensor wave patterns with known-good patterns. See DTC P0340: CAMSHAFT POSITION (CMP) SENSOR MALFUNCTION in appropriate SELF-DIAGNOSTICS article. If wave patterns are synchronized, both sensors are okay. If wave patterns are not synchronized, cam timing is incorrect. Repair as necessary and recheck wave pattern.
4. Remove CMP sensor. Without touching engine block, wave CMP sensor close enough to generate an output signal. If there is still no output signal from sensor, go to next step. If there is an output wave pattern, repeat step 2 . If step 2) has been repeated one time already, substitute a known-good ECM and recheck system. If symptom or indication goes away, replace original ECM.
5. Check for poor connections or loose wires between CMP sensor and ECM. See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000) . Repair as necessary and recheck. If no problems are found with wires or connectors, replace CMP sensor and recheck. Ensure wave pattern is okay.

CRANKSHAFT POSITION (CKP) SENSOR CIRCUIT

1. Check CKP sensor installation. Ensure sensor is secure, and that the heat shield and connector are correctly installed. If incorrect spacer is installed sensor will have either a weak signal or hit the reluctor ring. Remove CKP sensor and ensure tip is not bent or damaged. Repair or replace components as necessary.
2. Remove "D" plate from transmission bell housing and inspect condition of reluctor ring. Rotate engine and check runout of reluctor ring. If any teeth are bent or reluctor ring does not run true, replace reluctor ring and flywheel. After replacing reluctor ring check CKP sensor wave pattern. See DTC P0335 & P0336: CRANKSHAFT POSITION (CKP) SENSOR MALFUNCTION testing in appropriate SELF-DIAGNOSTICS article. If wave pattern is okay, repair is complete. If wave pattern is not okay, go to next step.
3. Check for poor connections or loose wires between CKP sensor and ECM. See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000) . Repair as necessary and recheck wave pattern. If wave pattern is okay, repair is complete. If wave pattern is not okay, go to next step.
4. Measure CKP sensor resistance between sensor terminals. Nominal sensor resistance is 1235-1365 ohms. If sensor resistance is not 1000-1600 ohms, replace CKP sensor and recheck CKP sensor wave pattern.

ENGINE COOLANT TEMPERATURE (ECT) SENSOR

Turn ignition off. Disconnect ECT sensor connector. Drain small amount of coolant. Remove ECT sensor from vehicle and measure resistance at various temperatures. Replace ECT sensor if not within specification. See ENGINE COOLANT TEMPERATURE SENSOR RESISTANCE table.

ENGINE COOLANT TEMPERATURE SENSOR RESISTANCE

ENGINE FUEL TEMPERATURE (EFT) SENSOR

EFT sensor is located on left side of engine, mounted to fuel rail. Turn ignition off and disconnect sensor connector. Remove EFT sensor from vehicle and measure resistance at various temperatures. Replace sensor if not within specification. See ENGINE FUEL TEMPERATURE SENSOR RESISTANCE table.

ENGINE FUEL TEMPERATURE SENSOR RESISTANCE

HEATED OXYGEN SENSOR (HO2S) CIRCUIT

There are 2 Primary Heated Oxygen Sensors (HO2S-1) located in front of each catalytic convertor. There are 2 Secondary Heated Oxygen Sensors (HO2S-2) located after each catalytic convertor. Start engine and bring to normal operating temperature. Compare wave patterns with known-good wave patterns. See P0150-P0153, P0156-P159, P0171-P0172, P0174-P0175, P1137-P1139, P1157-P1159, P1171-P1172 & P1185-P1196: HO2S CIRCUIT MALFUNCTION testing in appropriate SELF-DIAGNOSTICS article. See HEATED OXYGEN SENSOR VOLTAGE and HEATED OXYGEN SENSOR HEATER RESISTANCE tables.

HEATED OXYGEN SENSOR VOLTAGE

HEATED OXYGEN SENSOR HEATER RESISTANCE

INTAKE AIR TEMPERATURE (IAT) SENSOR

Intake air temperature sensor is located on air cleaner housing. Turn ignition off and disconnect sensor connector. Remove sensor from vehicle and measure resistance at various temperatures. Replace sensor if not within specification. See INTAKE AIR TEMPERATURE SENSOR RESISTANCE table.

INTAKE AIR TEMPERATURE SENSOR RESISTANCE

KNOCK SENSOR (KS)

There are 2 knock sensors located on either side of engine block. One mounted between cylinders No. 3 and 5, the other mounted between cylinders No. 2 and 4. Check for continuity between KS terminal and KS body. If continuity exists, replace KS.

MASS AIRFLOW SENSOR (MAF) CIRCUIT

1. In heavily polluted atmospheres MAF sensor may become contaminated causing incorrect voltage outputs. An air intake system that is restricted, has air leaks or missing components will cause incorrect voltage outputs. Turn ignition on. Measure voltage between ground and MAF sensor 3-pin connector terminal No. 1 (Brown/Orange wire). See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000) . If battery voltage does not exist, go to next step. If battery voltage exists, go to step 3 .
2. Measure voltage between ground and ECM Black 18-pin connector terminal No. 7 (Brown/Orange wire). If battery voltage does not exist, repair open or short in Brown/Orange wire between ECM and relay. See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000) . If battery voltage exists, repair open in Brown/Orange wire between MAF sensor and relay. See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000) .
3. Start engine and allow to idle. Backprobe MAF sensor 3-pin connector. Measure output voltage between sensor output terminal No. 2 (Blue/Green wire) and sensor ground terminal No. 3 (Red/Black wire). See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000) . Voltage output should increase as air flow increases. See «MASS AIRFLOW SENSOR OUTPUT VOLTAGE»(ref-3175-S21076084842000041800000) table.

MASS AIRFLOW SENSOR OUTPUT VOLTAGE

Scheme 26

PARK/NEUTRAL SWITCH

See IDLE CONTROL SYSTEM (GEMS) .

THROTTLE POSITION (TP) SENSOR

Note. TP sensor and fuel tank pressure sensor share a 5.0 volt reference voltage. A fuel tank pressure sensor failure that causes a short circuit will affect TP sensor output and set a TP sensor DTC.

Check TP sensor output voltage. See THROTTLE POSITION SENSOR SIGNAL VOLTAGE table. TP sensor output voltage should change smoothly as throttle position changes. Turn ignition off and disconnect TP sensor 3-pin connector. TP sensor resistance measured between terminals No. 1 and No. 3 should be 3200-4800 ohms. Replace TP sensor if output voltage or resistance is not as specified.

THROTTLE POSITION SENSOR VOLTAGE

VEHICLE SPEED SENSOR

See DTC P0500: VEHICLE SPEED SENSOR (VSS) SIGNAL OUT OF RANGE in appropriate SELF-DIAGNOSTICS article.

Note. It is physically possible to interchange the camshaft sprocket installed on vehicles equipped with GEMS ignition system and vehicles equipped with Bosch Motronic 5.2.1 ignition system. However, because the GEMS and Motronic systems are incompatible, an incorrect camshaft signal will be received by the ECM and DTC P0340 will set.

1. CMP sensor is located at the front of the engine block, above and behind the crankshaft pulley. CMP sensor is a magnetic switch used for switching battery voltage ON and OFF as slots in the camshaft sprocket pass by the sensor. This results in a 0.0-12.0 volt output signal sent as a square wave pattern to ECM 52-pin connector C0636 terminal No. 20 (Gray/Blue wire). (Scheme 24)and (Scheme 25). See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000).
2. Check for a CMP sensor wave pattern. If there is no wave pattern, go to next step. If wave pattern is not as specified, ensure correct cam sprocket is installed. Ensure that CMP sensor air gap between sensor and the side of the camshaft sprocket is less than 0.08" (2.0 mm) and that "O" ring is not damaged. Perform repairs as necessary.
3. Turn ignition off. Remove CMP sensor. Turn ignition on. Without touching engine block, wave CMP sensor close enough to generate an output signal. If no signal is generated, go to next step. If a signal is generated, ensure CMP sensor is correctly installed (install a NEW "O" ring) and check for excessive camshaft sprocket runout tolerance, excessive camshaft end-play, misaligned camshaft and crankshaft, incorrect speed signal correlation with CKP sensor signal or a magnetized camshaft sprocket.
4. Turn ignition off. Check for continuity in Black wire between CMP sensor 3-pin connector terminal No. 1 and ECM 52-pin connector C0636 terminal No. 17. If continuity exists, go to next step. If continuity does not exist, repair open in Black wire.
5. Turn ignition off. Check for continuity in Black wire between ground and CMP sensor 3-pin connector terminal No. 1 and ECM 52-pin connector C0636 terminal No. 17. If continuity exists, go to next step. If continuity does not exist, repair open in Black wire.
6. Turn ignition off. Check for continuity in Gray/Blue wire between CMP sensor 3-pin connector terminal No. 2 and ECM 52-pin connector C0636 terminal No. 20. If continuity exists, go to next step. If continuity does not exist, repair open in Gray/Blue wire.
7. Turn ignition on. Measure voltage between ground and CMP sensor 3-pin connector terminal No. 3 (Brown/Pink wire). If battery voltage is present, go to next step. On Discovery Series II, if battery voltage is not present, check fuse No. 2 (15-amp) located in engine compartment fuse/relay box. On Range Rover, if battery voltage is not present, check fuse No. 26 (20-amp) located in engine compartment fuse/relay box. On all models, if fuse is okay, check Brown/Pink wire. Perform repairs as necessary.

1. Check CKP sensor installation. Ensure sensor is secure, and that the heat shield and connector are correctly installed. If incorrect spacer is installed sensor will have either a weak signal or hit the reluctor ring. Remove CKP sensor and ensure tip is not bent or damaged. Repair or replace components as necessary.
2. Remove inspection plate from transmission bell housing and inspect condition of reluctor ring teeth. Rotate engine and check reluctor ring runout. If any teeth are bent or missing, or reluctor ring does not run true, replace reluctor ring and/or flywheel. After replacing reluctor ring check CKP sensor wave pattern. CKP sensor signal is a 0-300 mV AC that changes as engine speed increases and decreases. If wave pattern is okay, repair is complete. If wave pattern is not okay, go to next step.
3. Turn ignition off. Disconnect CKP sensor 3-pin connector and ECM 52-pin connector C0636. (Scheme 24)and (Scheme 25). See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000). Check for continuity between CKP sensor connector terminal No. 3 (Black wire) and ECM 52-pin connector C0636 terminal No. 45. If continuity exists, go to next step. If continuity does not exist, repair open in Black wire.
4. Turn ignition off. Check for continuity between ground and ECM 52-pin connector C0636 terminal No. 45 (Black wire). If continuity does not exist, go to next step. If continuity exists, repair short to ground in CKP sensor shield circuit. If sensor shield is not properly grounded a false or interrupted signal may be result.
5. Turn ignition off. Check for continuity between CKP sensor connector terminal No. 2 (Pink/Black wire) and ECM 52-pin connector C0636 terminal No. 46 (Pink/Black wire). If continuity exists, go to next step. If continuity does not exist, repair open or short in Pink/Black wire.
6. Turn ignition off. Check for continuity between CKP sensor connector terminal No. 1 (Black/Yellow wire) and ECM 52-pin connector C0636 terminal No. 32 (Black/Yellow wire). If continuity exists, go to next step. If continuity does not exist, repair open or short in Black/Yellow wire.
7. Turn ignition off. Reconnect ECM 52-pin connector C0636 and CKP sensor 3-pin connector. Turn ignition to START position. Check for a 0-300 mV AC signal at ECM 52-pin connector C0636 terminal No. 32 (Black/Yellow wire) as engine turns over. Voltage should vary and increase as engine speed increases with a peak voltage of approximately 300 mV. If signal voltage is not as specified, replace CKP sensor and recheck. If voltage is as specified, repair is complete.

Turn ignition off. Disconnect ECT sensor connector. Drain small amount of coolant. Remove ECT sensor from vehicle and measure resistance at various temperatures. Replace ECT sensor if not within specification. (Scheme 27)

Scheme 27

HEATED OXYGEN SENSOR (HO2S)

There are 2 primary Heated Oxygen Sensors (HO2S) located in front of each catalytic convertor. There are 2 secondary HO2S located after each catalytic convertor. Start engine an operate at normal operating temperature. Replace HO2S if output voltage is not as specified. See HEATED OXYGEN SENSOR (HO2S) OUTPUT VOLTAGE (BOSCH) table.

HEATED OXYGEN SENSOR (HO2S) OUTPUT VOLTAGE (BOSCH)

MASS AIRFLOW/INTAKE AIR TEMPERATURE (MAF/IAT) SENSOR CIRCUIT

1. Turn ignition off. Disconnect MAF/IAT sensor unit 5-pin connector. Turn ignition on and measure voltage between ground and connector terminal No. 2 (Brown/Pink wire). See WIRING DIAGRAMS article. If battery voltage is present, go to next step. If battery voltage is not present, check for an open or short in Brown/Pink wire between MAF/IAT sensor and fuse (No. 2, 15-amp on Discovery Series II or No. 26, 20-amp on Range Rover) located in engine compartment fuse/relay box. Perform repairs as necessary.
2. Turn ignition on and measure voltage between ground and MAF/IAT sensor connector terminal No. 4 (Red wire). If 5.0 volts is present, go to next step. If 5.0 volts is not present, check for an open or short in Red wire between MAF/IAT sensor and ECM 52-pin connector C0636 terminal No. 7. Perform repairs as necessary.
3. Turn ignition off. Check for continuity between ground and MAF/IAT sensor connector terminal No. 3 (Red/Black wire). If continuity exists, go to next step. If continuity does not exist, check for an open or short in Red/Black wire between MAF/IAT sensor and ECM 52-pin connector C0636 terminal No. 9. Perform repairs as necessary.
4. Turn ignition off and connect MAF/IAT sensor 5-pin connector. Start engine and allow to idle at normal operating temperature. Backprobe MAF/IAT sensor 5-pin connector terminal No. 1 (Gray/Light Green wire) and measure sensor output signal voltage. Output signal voltage should be approximately 0.0-5.0 volts and increase as engine speed and airflow increase. (Scheme 28) If voltage is as specified, go to next step. If voltage is not as specified, replace MAF sensor and retest.
5. Start engine and allow to idle at normal operating temperature. Backprobe ECM 52-pin connector C0636 terminal No. 34 (Gray/Light Green wire) measure sensor output signal voltage. Output signal voltage should be approximately 0.0-5.0 volts and increase as engine speed and airflow increases. (Scheme 28) If voltage is as specified, go to next step. If voltage is not as specified, check Gray/Light Green wire for an open or short between MAF/IAT sensor and ECM. Check for poor connections, loose terminals, and wires. Perform repairs as necessary.
6. Turn ignition off and connect MAF/IAT sensor 5-pin connector. Start engine and allow to idle at normal operating temperature. Backprobe MAF/IAT sensor 5-pin connector terminal No. 5 (Blue/Green wire) and measure sensor output signal voltage. Output signal voltage should be approximately 0.0-5.0 volts and increase as engine speed and airflow increase. (Scheme 29)table. If voltage is as specified, go to next step. If voltage is not as specified, replace MAF sensor and retest.
7. Start engine and allow to idle at normal operating temperature. Backprobe ECM 52-pin connector C0636 terminal No. 23 (Blue/Green wire) measure sensor output signal voltage. Output signal voltage should be approximately 0.0-5.0 volts and increase as engine speed and airflow increases. (Scheme 29) If voltage is not as specified, check Blue/Green wire for an open or short between MAF/IAT sensor and ECM. Check for poor connections, loose terminals, and wires. Perform repairs as necessary.

Scheme 28

Scheme 29

Ensure KS mounting bolt is tightened to 16 ft. lbs. (22 N.m). Check for poor connections, loose terminals, and open or shorted wires. See WIRING DIAGRAMS .

Note. Because ECM is able to determine the closed throttle position, the TP sensor does not need to be adjusted when replaced.

1. Check for poor connections, loose terminals, and open or shorted wires. See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000) . If no problems are found, go to next step. Perform repairs as necessary.
2. Turn ignition on. Backprobe between ECM 52-pin connector C0636 terminals No. 24 (Yellow/Light Green wire) and No. 25 (Red/Black wire). Measure voltage while moving throttle valve between fully closed (idle) and fully open (wide open) positions. See «THROTTLE POSITION SENSOR SIGNAL VOLTAGE»(ref-3175-S12198401832000041800000) table. If voltage is as specified and changes smoothly, test is complete. If voltage is not as specified, replace TP sensor.

THROTTLE POSITION SENSOR SIGNAL VOLTAGE

CANISTER PURGE SOLENOID (DISCOVERY)

Measure resistance between canister purge solenoid terminals. See WIRING DIAGRAMS . Resistance should be approximately 22-40 ohms. Replace canister purge solenoid if resistance is not as specified.

Discovery

Fuel injector solenoid resistance should by approximately 15.7-16.7 ohms at 68°F (20°C).

Discovery Series II & Range Rover

Fuel injector solenoid `resistance should be approximately 13.8-15.2 ohms at 68°F (20°C).

1. Fuel pump relay is an integral component of the multifunction relay unit, which is located in right rear of engine compartment. Disconnect connectors at multifunction relay unit. Check continuity with ohmmeter positive probe connected to multifunction relay unit 6-pin Black connector C1030 terminal No. 2 and negative probe connected to multifunction relay unit 6-pin Black connector C1030 terminal No. 1. (Scheme 31) Continuity should exist. If continuity is as specified, go to next step. If continuity is not as specified, replace multifunction relay unit.
2. Reverse polarity of the ohmmeter. Continuity should not exist. If continuity is as specified, go to next step. If continuity is not as specified, replace multifunction relay unit.
3. Check continuity between multifunction relay unit 9-pin Black connector C1029 terminals No. 7 and 4. (Scheme 30) Continuity should not exist. If continuity is as specified, go to next step. If continuity is not as specified, replace multifunction relay unit.
4. Apply battery voltage to multifunction relay unit 6-pin Black connector C1030 terminal No. 2 and ground multifunction relay unit 6-pin Black connector C1030 terminal No. 1. Check continuity between multifunction relay unit 9-pin Black connector C1029 terminals No. 7 and 4. Continuity should exist. If continuity is as specified, fuel pump relay is okay. If continuity is not as specified, replace multifunction relay unit.

Scheme 30

Scheme 31

1. Fuel pump relay is an integral component of the multifunction relay unit, which is located in right rear of engine compartment. Before checking fuel pump relay, check inertia fuel shut-off switch located on engine compartment firewall. Check for continuity between inertia fuel shut-off switch White/Purple wire terminals. If continuity exists, go to next step. If continuity does not exist, depress inertia fuel shut-off switch plunger to reset switch. If continuity still does not exist, replace inertia fuel shut-off switch.
2. Turn ignition off. Disconnect ECM Black 36-pin and 18-pin connectors. Turn ignition on. Measure voltage between ground and multifunction relay unit 6-pin connector terminal No. 2 (White/Green wire). See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000). If battery voltage exists, go to step 4. If battery voltage does not exist, go to next step.
3. If battery voltage does not exist, check fuse No. 3 (20-amp), located in satellite fuse/relay box No. 1 behind fascia, left of steering column. If fuse is okay, repair open in White/Green wire. If fuse is not okay, repair short in White/Green wire and replace fuse. See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000).
4. Using a backprobe set, measure voltage between ground and ECM Black 18-pin connector terminal No. 8 (White/Green wire). (Scheme 23) See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000). If battery voltage exists, go to next step. If battery voltage does not exist, repair open in White/Green wire.
5. Ensure ignition is on. Measure voltage between ground and multifunction relay unit 8-pin connector terminal No. 7 (Purple/White wire). See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000). If battery voltage exists, go to next step. If battery voltage does not exist, check fuse No. 6 (15-amp). If fuse is not okay, repair short in Purple/White wire and replace fuse. If fuse is okay, check for an open in Purple/White wire. Repair as necessary. If Purple/White wire is okay, repair open or short in power supply circuit between battery and fuse No. 6. See POWER DISTRIBUTION in «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000).
6. Turn ignition off. Using a fused jumper wire and backprobe set, connect ECM Black 36-pin connector terminal No. 24 (Blue/Purple wire) to ground. (Scheme 26) See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000). Turn ignition on. Check fuel pump operation. If fuel pump is not operating, go to next step. If fuel pump is operating, substitute a known-good ECM and recheck for original symptom or indication. If symptom or indication goes away, replace original ECM.
7. Measure voltage between ground and multifunction relay unit 8-pin connector terminal No. 4 (White/Purple wire). See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000). If battery voltage exists, repair open in circuit between multifunction relay unit, inertia fuel shut-off switch and fuel pump. If battery voltage does not exist, replace fuel pump relay and recheck.

Discovery Series II

1. Ensure main relay is operating properly. See «Main Relay (Discovery Series II)»(ref-3175-S19357419312000041800000) . Remove fuel pump relay. Turn ignition on. Measure voltage between ground and fuel pump relay connector terminal No. 85. If battery voltage is present, go to next step. If battery voltage is not present, check for continuity between fuel pump relay connector terminal No. 85 and main relay connector terminal No. 87. If continuity does not exist, repair or replace engine compartment fuse/relay box.
2. Turn ignition off. Check for continuity between fuel pump relay connector terminal No. 86 and ECM 24-pin connector C0635 terminal No. 18 (Blue/Purple wire). If continuity exists, go to next step. If continuity does not exist, repair open in Blue/Purple wire. See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000) .
3. Turn ignition off. Measure voltage between ground and fuel pump relay connector terminal No. 30. If battery voltage is present, go to next step. If battery voltage is not present, check fuse No. 10 (30-amp). If fuse is blown, go to next step. If fuse is okay, check for continuity in fuse/relay box circuit between fuel pump relay connector terminal No. 30 and battery voltage supply Red wire connection. If continuity does not exist, repair or replace engine compartment fuse/relay box.
4. If fuse No. 10 (30-amp) is blown, check for a short in White/Purple wire between fuel pump relay in engine compartment fuse/relay box and fuel pump connector terminal No. 1. Perform repairs as necessary. See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000) .
5. Check for continuity between fuel pump relay terminals No. 1 and 2. If continuity exists, go to next step. If continuity does not exist, replace fuel pump relay.
6. Check for continuity between fuel pump relay terminals No. 3 and 5. If continuity does not exist, go to next step. If continuity exists, replace fuel pump relay.
7. Using a fused jumper wire, connect battery voltage to fuel pump relay terminal No. 1. Using another jumper wire, connect fuel pump relay terminal No. 2 to ground. When fuel pump relay is energized, check for continuity between fuel pump relay terminals No. 3 and 5. If continuity does not exist, replace fuel pump relay.

Range Rover

1. Fuel pump relay is in engine compartment fuse/relay box, which is located on right side of engine compartment. Before checking fuel pump relay, check inertia fuel shut-off switch located on engine compartment firewall. Check for continuity between inertia fuel shut-off switch terminals No. 1 (White/Orange wire) and No. 3 (White/Blue wire). If continuity exists, go to next step. If continuity does not exist, depress inertia fuel shut-off switch plunger to reset switch. If continuity still does not exist, replace inertia fuel shut-off switch.
2. Turn ignition on. Measure voltage between ground and fuel pump relay terminal No. 1, located in engine compartment fuse/relay box. See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000). If battery voltage exists, go to next step. If battery voltage does not exist, repair power supply circuit between fuse/relay box and battery.
3. Turn ignition off. Measure voltage between ground and fuel pump relay terminal No. 3. If battery voltage exists, go to next step. If battery voltage does not exist, check fuse No. 39 (20-amp). If necessary, replace fuse, and repair power supply circuit between fuse/relay box and battery. See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000).
4. Turn ignition off. Disconnect ECM connectors. Check for continuity in Blue/Purple wire between engine compartment fuse/relay box and ECM 24-pin connector C0635 terminal No. 18. (Scheme 24)and (Scheme 25). See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000). If continuity exists, go to next step. If continuity does not exist, repair open in Blue/Purple wire.
5. Check for continuity between fuel pump relay terminals No. 1 and 2. If continuity exists, go to next step. If continuity does not exist, replace fuel pump relay.
6. Check for continuity between fuel pump relay terminals No. 3 and 5. If continuity does not exist, go to next step. If continuity exists, replace fuel pump relay.
7. Using a fused jumper wire, connect battery voltage to fuel pump relay terminal No. 1. Using another jumper wire, connect fuel pump relay terminal No. 2 to ground. When fuel pump relay is energized, check for continuity between fuel pump relay terminals No. 3 and 5. If continuity does not exist, replace fuel pump relay.

IDLE SPEED CONTROL (ISC) STEPPER MOTOR

See IDLE CONTROL SYSTEM (GEMS) .

1. Main relay may also be called the Multiport Fuel Injection Load relay. Main relay is an integral component of the multifunction relay unit, which is located in right rear of engine compartment. Disconnect connectors at multifunction relay unit. Check continuity with ohmmeter positive probe connected to multifunction relay unit 9-pin Black connector C1029 terminal No. 6 and negative probe connected to multifunction relay unit 6-pin Black connector C1030 terminal No. 3. (Scheme 30)and (Scheme 31). Continuity should exist. If continuity is as specified, go to next step. If continuity is not as specified, replace multifunction relay unit.
2. Reverse polarity of the ohmmeter. Continuity should not exist. If continuity is as specified, go to next step. If continuity is not as specified, replace multifunction relay unit.
3. Check continuity between multifunction relay unit 9-pin Black connector C1029 terminals No. 6 and 8, and between terminals No. 6 and 3. Continuity should not exist. If continuity is as specified, go to next step. If continuity is not as specified, replace multifunction relay unit.
4. Apply battery voltage to multifunction relay unit 9-pin Black connector C1029 terminal No. 6 and ground multifunction relay unit 6-pin Black connector C1030 terminal No. 3. Check continuity between multifunction relay unit 9-pin Black connector C1029 terminals No. 6 and 8, and between terminal No. 6 and 3. Continuity should exist. If continuity is as specified, fuel pump relay is okay. If continuity is not as specified, replace multifunction relay unit.

1. Main relay may also be called the Multiport Fuel Injection Load relay. Main relay is an integral component of the multifunction relay unit, which is located in right rear of engine compartment.
2. Using a backprobe set, measure voltage between ground and multifunction relay unit 8-pin connector terminal No. 6 (Brown/Light Green wire). See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000). If battery voltage exists, go to step 4. If battery voltage does not exist, check fuse No. 7 (20-amp). If fuse is okay, go to next step. If fuse is not okay, repair short in Brown/Light Green wire and replace fuse.
3. Measure voltage on battery side of fuse No. 7 (20-amp). See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000). If battery voltage exists, repair open in Brown/Light Green wire. If battery voltage does not exist, repair power supply circuit from battery. See appropriate wiring diagram in POWER DISTRIBUTION article in ACCESSORIES & EQUIPMENT.
4. Disconnect negative battery cable. Disconnect ECM Black 36-pin and 18-pin connectors. Check for continuity in Blue/Red wire between ECM Black 18-pin connector terminal No. 17 and multifunction relay unit 6-pin connector terminal No. 3. (Scheme 23) See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000). If continuity exists, go to next step. If continuity does not exist, repair open or short in Blue/Red wire.
5. Using a backprobe set, check for continuity between multifunction relay unit 8-pin connector terminals No. 6 (Brown/Light Green wire) and No. 3 (Brown/Orange wire), and between terminals No. 6 and No. 8 (Brown/Orange wire). If continuity does not exist, go to next step. If continuity exists, remove main relay and recheck relay unit for continuity between specified terminals. If continuity does not exist, go to step 8. If continuity exists, repair or replace multifunction relay unit.
6. Reconnect negative battery cable. Using a backprobe set, connect ECM Black 18-pin connector terminal No. 17 (Blue/Red wire) to ground. (Scheme 23) See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000). Measure voltage between ground and multifunction relay unit 8-pin connector terminals No. 3 (Brown/Orange wire) and No. 8 (Brown/Orange wire), individually. See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000).
7. If battery voltage exists at both terminals, substitute a known-good ECM and retest for original symptom or indication. If symptom or indication goes away, replace original ECM. If battery voltage does not exist, replace main relay and retest. If battery voltage still does not exist, check multifunction relay unit internal circuits. See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000). Repair or replace multifunction relay unit as necessary.
8. Remove main relay. Check for continuity between main relay coil terminals. See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000). If continuity exists, go to next step. If continuity does not exist, replace main relay.
9. Using a fused jumper wire, connect battery voltage and ground to main relay coil terminals. Check for continuity between main relay switch terminals. See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000). If continuity exists, main relay is operating properly. If continuity does not exist, replace main relay. Remove battery ground and check for continuity between main relay switch terminals. If continuity exists, replace main relay.

1. Main relay may also be called the engine main control relay. Main relay is in the engine compartment fuse/relay box which is located at the right side of the engine compartment. Battery voltage is supplied directly to engine compartment fuse/relay box through Red wire from battery.
2. Before checking main relay, check inertia switch located on engine compartment firewall. Check for continuity between inertia switch terminals No. 1 (Brown/Black wire) and No. 3 (White/Green wire). If continuity exists, go to next step. If continuity does not exist, depress inertia switch plunger to reset switch. If continuity still does not exist, replace inertia switch.
3. Turn ignition off. Remove main relay from engine compartment fuse/relay box. Measure voltage between ground and main relay connector terminal No. 85. See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000) . If battery voltage is present, go to step 4 . If battery voltage is not present, check fuse No. 13 (15-amp) located in engine compartment fuse/relay box. Preform repairs as necessary. If fuse is okay, go to next step.
4. Measure voltage between ground and main relay connector terminal No. 30. See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000) . If battery voltage is present, go to next step. If battery voltage is not present, repair open in circuit between main relay and battery. If circuit can not be repaired, replace engine compartment fuse/relay box.
5. Using a backprobe set, check for continuity between main relay connector terminal No. 86 and ECM 24-pin connector terminal No. 23 (Blue/Red wire). See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000) . If continuity exists, go to next step. If continuity does not exist, repair open in circuit between main relay and ECM.
6. Check for continuity between main relay terminals No. 85 and 86. If continuity exists, go to next step. If continuity does not exist, replace main relay.
7. Check for continuity between main relay terminals No. 30 and 87. If continuity does not exist, go to next step. If continuity exists, replace main relay.
8. Using a fused jumper wire, connect battery voltage to main relay terminal No. 85. Using another jumper wire, connect main relay terminal No. 86 to ground. When main relay is energized, check for continuity between main relay terminals No. 30 and 87. If continuity does not exist, replace main relay.

1. Main relay may also be called the engine main control relay. Main relay is in the engine compartment fuse/relay box which is located at the right side of the engine compartment. Battery voltage is supplied directly to engine compartment fuse/relay box through Red wire from battery.
2. Turn ignition off. Remove main relay from engine compartment fuse/relay box. Measure voltage between ground and main relay connector terminals No. 1 and 3. See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000) . If battery voltage is present at both terminals, go to next step. If battery voltage is not present, check for an open in Red wire between battery and engine compartment fuse/relay box. Repair as necessary. If Red wire is okay, repair or replace engine compartment fuse/relay box.
3. Check for continuity between main relay terminals No. 1 and 2. If continuity exists, go to next step. If continuity does not exist, replace main relay.
4. Check for continuity between main relay terminals No. 3 and 5. If continuity does not exist, go to next step. If continuity exists, replace main relay.
5. Using a fused jumper wire, connect battery voltage to main relay terminal No. 1. Using another jumper wire, connect main relay terminal No. 2 to ground. When main relay is energized, check for continuity between main relay terminals No. 3 and 5. If continuity does not exist, replace main relay.

FUEL SYSTEM PRESSURE RELEASE

Fuel pressure can be released at either the fuel supply line at the fuel rail or at the fuel filter. Position shop towel around fitting to protect against fuel spray. Carefully loosen fitting. When fuel pressure has been released, tighten fitting.

FUEL CONTROL

Fuel Pump Current Draw

The maximum fuel pump current draw should be 6.5 amps at 12.5 volts.

Turn ignition off. Disconnect IAC valve 4-pin connector. Measure resistance of IAC valve motor coils between terminals "A" and "D", and between "B" and "C". See WIRING DIAGRAMS . If resistance either coil is not 51-55 ohms, replace IAC valve and ensure warm idle position is 20-30 steps.

Turn ignition on. Using a backprobe set, measure voltage at ECM Red 36-pin connector terminal No. 18 (Orange/Black wire). With shift lever in Park or Neutral voltage should be zero. With shift lever in Drive, battery voltage should exist.

IDLE AIR CONTROL VALVE CIRCUIT (IACV)

Note. The ECM sets engine cold start idle speed and default idle speed at 1200 RPM. Although the engine idle speed is the same, one condition represents normal engine operation and the other does not.

1. IACV has a 3-pin connector and is located on the side of the intake air duct. IACV is used to maintain good quality idle speed under all operating conditions. IACV has 2 coils that use opposing PWM signals to control the open or closed positions of a rotary valve. IACV OPEN PWM signal is sent from ECM 52-pin connector C0636 terminal No. 42 (Red/Green wire). IACV CLOSE PWM signal is sent from ECM 52-pin connector C0636 terminal No. 43 (Blue/Gray wire). If one of the PWM signals fails, the ECM closes down the remaining signal causing the IACV to revert to a default position.
2. Check for an intake air system air leak. Check for blocked, restricted or crimped IACV actuator port or hoses.
3. Turn ignition off. Disconnect IACV 3-pin connector. Turn ignition on. Measure voltage between ground and IACV 3-pin connector terminal No. 2 (Brown/Orange wire). If battery voltage is present, go to step 5 . On Discovery Series II, if battery voltage is not present, check fuse No. 2 (15-amp) located in engine compartment fuse/relay box. On Range Rover, if battery voltage is not present, check fuse No. 37 (30-amp). On all models, if fuse is okay, go to next step. If fuse is not okay, replace fuse and recheck component operation.
4. Turn ignition off. Check for continuity in Brown/Orange wire between fuse and IACV 3-pin connector terminal No. 2. If continuity does not exist, repair Brown/Orange wire as necessary. If continuity exists, check main relay operation and circuit between fuse and ignition switch. Perform repairs as necessary.
5. Turn ignition off. Check for continuity in Red/Green wire between IACV 3-pin connector terminal No. 1 and ECM 52-pin connector C0636 terminal No. 43. If continuity exists, go to next step. If continuity does not exist, repair Red/Green wire as necessary.
6. Turn ignition off. Check for continuity in Blue/Gray wire between IACV 3-pin connector terminal No. 3 and ECM 52-pin connector C0636 terminal No. 42. If continuity exists, go to next step. If continuity does not exist, repair Blue/Gray wire as necessary.
7. Turn ignition off. Using a fused jumper wire, connect battery voltage to IACV terminal No. 2 (Brown/Orange wire). Using another jumper wire, alternately ground IACV terminals No. 1 (Red/Green wire) and No. 3 (Blue/Gray wire). Replace IACV if IACV actuator operation can not be detected.

IGNITION SYSTEM

Note. For basic ignition checks, see BASIC DIAGNOSTIC PROCEDURES article.

TIMING CONTROL SYSTEMS

Note. Ignition timing is controlled by Land Rover's Generic Engine Management System (GEMS) or Bosch Motronic 5.2.1 and is not adjustable.

ADVANCED EVAP SYSTEM (DISCOVERY)

Note. Temperature differences between vehicle and test equipment can cause misleading test results because of expansion and contraction of test gases during test. Ensure vehicle and test equipment temperatures are similar.

1. When the engine is started, the ECM checks the engine coolant temperature. If Engine Coolant Temperature (ECT) indicates that coolant temperature is less than 131°F (55°C), ECM will activate the Secondary Air Injection (SAI) system. Ensure ECT sensor is operating properly.
2. ECT sensor ground is at ECM 52-pin connector C0636 terminal No. 21 (Red/Black wire). ECT sensor input analog 0-5 volt signal is at ECM 52-pin connector C0636 terminal No. 22 (Green wire). (Scheme 24)and (Scheme 25). See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000). (Scheme 32)
3. Battery voltage is supplied to the inertia switch via fuse No. 13 (10-amp) located in the engine compartment fuse/relay box. When inertia switch is closed, battery voltage is supplied to main relay coil. Main relay operation is controlled through ECM main relay coil ground at ECM 24-pin connector C0635 terminal No. 23 (Blue/Red wire). Ensure main relay is operating properly.
4. When main relay is energized, battery voltage is supplied to SAI pump relay coil via fusible link No. 2 (50-amp) located in the engine compartment fuse/relay box. SAI pump relay operation is controlled through ground at ECM 52-pin connector C0636 terminal No. 16 (Black/Orange wire).
5. When the main relay is energized, battery voltage is supplied the SAI vacuum solenoid valve via fuse No. 2 (15-amp) located in engine compartment fuse/relay box. SAI vacuum solenoid valve operation is controlled through ground at ECM 52-pin connector C0636 terminal No. 4 (Black/Blue wire). SAI vacuum solenoid valve is energized at the same time as the SAI air pump is energized.

Scheme 32

1. When the engine is started, the ECM checks the engine coolant temperature. If Engine Coolant Temperature (ECT) indicates that coolant temperature is less than 131°F (55°C), ECM will activate the Secondary Air Injection (SAI) system. Ensure ECT sensor is operating properly.
2. ECT sensor ground is at ECM 52-pin connector C0636 terminal No. 21 (Red/Black wire). ECT sensor input analog 0-5 volt signal is at ECM 52-pin connector C0636 terminal No. 22 (Green/Blue wire). (Scheme 24)and (Scheme 25). See «WIRING DIAGRAMS»(ref-3175-S42626799842004042000000). (Scheme 33)
3. When SAI pump relay is energized, battery voltage is supplied to relay coil connector terminal No. 5 via fusible link No. 2 (50-amp) located in the engine compartment fuse/relay box. SAI pump relay operation is controlled through ground at ECM 52-pin connector C0636 terminal No. 16 (Brown/Green wire).
4. When the main relay is energized, battery voltage is supplied to SAI vacuum solenoid valve connector terminal No. 1 (Brown/Pink wire) via fuse No. 26 (20-amp) located in engine compartment fuse/relay box. SAI vacuum solenoid valve operation is controlled through ground at ECM 52-pin connector C0636 terminal No. 4 (Pink/Blue wire). SAI vacuum solenoid valve is energized at the same time as the SAI air pump is energized.

Scheme 33

MISCELLANEOUS CONTROLS

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

When A/C switch is turned on, a 12-volt A/C request signal will be seen at ECM Red 36-pin connector terminal No. 28 (Yellow/Black wire). When ECM confirms proper system operating conditions, a 12-volt A/C grant signal will be seen at ECM Black 36-pin connector terminal No. 1 (Black/Gray wire).

When A/C switch is turned on, an A/C request signal will be seen at ECM 40-pin connector C0637 terminal No. 16 (Yellow/Gray wire) and terminal No. 38 (Yellow/Black wire). The operation of the ATC request is via A /C switch being connected to ground.