Engine Controls - Self-Diagnostics - with Codes Land Rover Discovery L318

DATA LINK CONNECTOR (DLC) LOCATION

On all models, Data Link Connector (DLC) is a 16-pin connector. (Scheme 6) On Discovery Series II, DLC is located under steering wheel. On Range Rover, DLC is located in passenger footwell.

Scheme 6

ECM CONNECTOR IDENTIFICATION

On Discovery Series II, ECM is located on the right side "A" post behind the front passenger kick panel. On Range Rover, the ECM is mounted in a plastic E-box located on the left side of engine compartment firewall. ECM is cooled by a dedicated fan, which provides cabin air to the plastic E-box maintaining a suitable environment for ECM operation. The operating temperature of the ECM is monitored by an internal temperature sensor. On all models, the ECM has 5 independent connectors totalling 134 pins. (Scheme 7)and (Scheme 8). See ECM CONNECTOR IDENTIFICATION table.

Scheme 7

Scheme 8

ECM CONNECTOR IDENTIFICATION

DIAGNOSTIC TESTS (BOSCH)

Note. After each DTC repair has been completed a specific repair confirmation test drive cycle is required to confirm repair. See REPAIR CONFIRMATION DRIVE CYCLE .

DIAGNOSTIC TROUBLE CODES (DTC) LIST

REPAIR PROCEDURE

Begin all repairs by retrieving Diagnostic Trouble Codes (DTCs) and confirming customer complaint. See DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION (BOSCH) table in SELF-DIAGNOSTICS - INTRODUCTION article. After repairs are completed, allow engine to cool and perform specified repair confirmation drive cycle. See REPAIR CONFIRMATION DRIVE CYCLE .

RELIEVING FUEL PRESSURE

Fuel pressure can be relieved at fuel feed fitting at fuel rail. Position cloth around fitting to catch fuel spray. Using 2 wrenches, loosen fitting. On Range Rover, tighten fuel feed fitting to 12 ft. lbs. (16 N.m). On Discovery Series II, tighten fuel feed fitting to 84 INCH lbs. (9.5 N.m).

REPAIR CONFIRMATION DRIVE CYCLE

Note. It is important to follow each instruction for each repair confirmation drive cycle. Failure to perform each instruction under conditions and time period specified may require repeating confirmation test drive. Before turning ignition switch to OFF position at completion of confirmation test drive, recheck for any Diagnostic Trouble Codes (DTCs) using Land Rover TestBook or OBD-II scan tool.

Repair Confirmation Drive Cycle "A"

1. After completing DTC and/or complaint repairs, allow engine to cool. Install Land Rover TestBook or OBD-II scan tool. Turn ignition on for 30 seconds. Ensure Engine Coolant Temperature (ECT) sensor indicates less than 140°F (60°C).
2. Start engine and allow to idle for 2 minutes. Check for DTCs using Land Rover TestBook or OBD-II scan tool. If any DTC is indicated, perform specified repairs. See DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION (BOSCH) table in SELF-DIAGNOSTICS - INTRODUCTION article. If no DTCs are indicated, repair is complete.

Repair Confirmation Drive Cycle "B"

1. After completing DTC and/or complaint repairs allow engine to cool. Install Land Rover TestBook or OBD-II scan tool. Turn ignition on for 30 seconds. Ensure Engine Coolant Temperature (ECT) sensor indicates less than 140°F (60°C).
2. Start engine and allow to idle for 2 minutes. Perform 2 light accelerations from zero to 35 MPH using light pedal pressure and slow to a stop. Perform 2 medium accelerations from zero to 45 MPH using moderate pedal pressure and slow to a stop. Perform 2 hard accelerations from zero to 55 MPH using heavy pedal pressure and slow to a stop.
3. Allow engine to idle for 2 minutes. Check for DTCs using Land Rover TestBook or OBD-II scan tool. If any DTC is indicated, perform specified repairs. See DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION (BOSCH) table in SELF-DIAGNOSTICS - INTRODUCTION article. If no DTCs are indicated, repair is complete.

Repair Confirmation Drive Cycle "C"

1. After completing DTC and/or complaint repairs allow engine to cool. Install Land Rover TestBook or OBD-II scan tool. Turn ignition on for 30 seconds. Ensure Engine Coolant Temperature (ECT) sensor indicates less than 140°F (60°C).
2. Start engine and allow to idle for 2 minutes. Perform 2 light accelerations from zero to 35 MPH using light pedal pressure and slow to a stop. Perform 2 medium accelerations from zero to 45 MPH using moderate pedal pressure and slow to a stop. Perform 2 hard accelerations from zero to 55 MPH using heavy pedal pressure. When second acceleration cycle is completed, increase vehicle speed to 60 MPH and cruise for 8 minutes. Reduce speed to 50 MPH, continue cruising for another 3 minutes and slow to a stop.
3. Allow engine to idle for 3 minutes. Check for DTCs using Land Rover TestBook or OBD-II scan tool. If any DTC is indicated, perform specified repairs. See DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION (BOSCH) table in SELF-DIAGNOSTICS - INTRODUCTION article. If no DTCs are indicated, repair is complete.
4. The following areas have an associated readiness test which must be confirmed as complete, before a problem resolution can be verified: Catalytic converter fault. Evaporative loss system fault. HO2S sensor fault. HO2S sensor heater fault. When carrying out Confirmation Drive Cycle "C" to determine a fault in any of the above areas, select the TestBook readiness test icon to verify that the test has been confirmed as complete.

Repair Confirmation Drive Cycle "D"

Note. The final phase of Repair Confirmation Drive Cycle: "D" requires that a flat, straight route be chosen that allows a vehicle speed of 35 MPH to be maintained without stopping or excessive pedal pressure.

1. After completing DTC and complaint repairs allow engine to cool. Install Land Rover TestBook or OBD-II scan tool. Turn ignition on for 30 seconds. Ensure Engine Coolant Temperature (ECT) sensor indicates less than 95°F (35°C).
2. Start engine and allow to idle for 2 minutes. Perform 2 light accelerations from zero to 35 MPH using light pedal pressure and slow to a stop. Perform 2 medium accelerations from zero to 45 MPH using moderate pedal pressure and slow to a stop. Perform 2 hard accelerations from zero to 55 MPH using heavy pedal pressure. Increase speed to 60 MPH and cruise for 5 minutes. Reduce speed to 50 MPH, continue to cruise for 5 minutes. Reduce speed to 35 MPH, continue to cruise for 5 minutes and slow to a stop.
3. Allow engine to idle for 2 minutes. Check for DTCs using Land Rover TestBook or OBD-II scan tool. If any DTC is indicated, perform specified repairs. See DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION (BOSCH) table in SELF-DIAGNOSTICS - INTRODUCTION article. If no DTCs are indicated, repair is complete.

Repair Confirmation Drive Cycle "E"

Note. While performing REPAIR CONFIRMATION DRIVE CYCLE "E" ensure engine does not overheat. DO NOT turn ignition off until after check for DTCs is completed.

1. After completing DTC and/or complaint repairs, allow engine to cool. Install Land Rover TestBook or OBD-II scan tool. Ensure Engine Coolant Temperature (ECT) sensor indicates less than 140°F (60°C). Ensure fuel tank is more than a quarter full.
2. Start engine and allow to idle undisturbed for 20 minutes. DO NOT turn ignition off. Check for DTCs using Land Rover TestBook or OBD-II scan tool. If any DTC is indicated, perform specified repairs. See DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION (BOSCH) table in SELF-DIAGNOSTICS - INTRODUCTION article. If no DTCs are indicated, repair is complete.

Description

DTCs P0100 and P0101 will set based on compared signals from the Mass Airflow (MAF)/Intake Air Temperature (IAT) sensors and the Throttle Position (TP) sensor. DTC P0100 will set if there is a mass or volume airflow circuit malfunction. If P0100 is set go to DTC P0102 & P0103: MASS OR VOLUME AIRFLOW CIRCUIT LOW/HIGH INPUT testing. DTC P0101 is a load monitoring DTC based on an unexpected throttle position ratio to airflow. DTC P0101 will set if there is a mass or volume airflow circuit range or performance problem. If DTC P0101 is set go to DTC P0120, P0122 & P0123: THROTTLE POSITION (TP) SENSOR CIRCUIT testing.

Note. Mass Airflow (MAF) and Intake Air Temperature (IAT) sensors are combined into a single unit and located between the air filter housing and the intake manifold. ECM uses input signals from the MAF/IAT sensor unit to calculate volume of air flowing into the engine.

MAF sensor uses a hot-film element to monitor mass of airflow being drawn into engine. There are 2 sensing elements, one element monitors ambient air temperature, while the other is heated to a temperature 360°F (200°C) more than ambient air temperature. When intake air passes the heated element, the temperature decreases, reducing the resistance of the hot-film element. In order to maintain the set temperature, the heated element circuit must supply more current. Changes in current are detected in the monitoring circuit. This change data is supplied to the ECM as a voltage between 0.0-5.0 volts. ECM interprets this data as a measure of the mass of airflow. The measured mass of airflow is used by the ECM to determine the amount of fuel to be injected for optimum engine performance and low emissions.

ECM checks MAF sensor for open circuit and confirms expected sensor output voltage at specific engine speeds. ECM will use a default value for airflow based on throttle position, engine speed and intake air temperature. A MAF sensor failure will result in hard engine starts, engine stalling after starting, engine idle speed control inoperative, poor throttle response and driveability, emissions control inoperative, MAF sensor signal offset, reduced engine performance, and/or a high long term fuel correction.

MAF sensor can fail or supply an incorrect signal in the following ways

1. Open in sensor harness.
2. Short to battery voltage in sensor harness.
3. Short to ground in sensor harness.
4. Contaminated or damaged sensor element.
5. Air leak after the MAF sensor.
6. Inlet air restriction.
7. Resistance in wiring harness causing signal offset.

Diagnostic Aids

1. If DTC P0102 is set, MAF sensor signal is less than minimum threshold for specific speed range. Engine speed must be greater than 200 RPM for more than 300 mS and remain greater than 400 RPM. MAF signal must be less than threshold mapped when compared with engine speed for more than 500 mS.
2. If DTC P0103 is set, MAF sensor signal is greater than maximum threshold for specific speed range. Engine speed must be greater than 200 RPM for more than 10 mS. MAF signal must be greater than threshold mapped when compared with engine speed for longer than 300 mS.

Diagnosis & Repair

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). (Scheme 9) See appropriate wiring diagram in 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. When repairs are complete, go to step 6.
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 C0636, 52-pin connector terminal No. 7. Perform repairs as necessary. When repairs are complete, go to step 6.
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 C0636, 52-pin connector terminal No. 9. Perform repairs as necessary. When repairs are complete, go to step 6.
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. 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. If voltage is as specified, go to next step. If voltage is not as specified, replace MAF sensor and retest. When repairs are complete, go to step 6.
5. 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. If voltage is as specified, go to next step. 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. When repairs are complete, go to next step.
6. When DTC P0102 or P0103 repairs are completed, perform «REPAIR CONFIRMATION DRIVE CYCLE "A"»(/land-rover/discovery/l318-1998-2002/remont/testing-diagnostics/#engine-controls-self-diagnostics-with-codes__repair-confirmation-drive-cycle-a).

Scheme 9

DTC P0111, P0112, P0113: INTAKE AIR TEMPERATURE (IAT) SENSOR CIRCUIT

Note. Mass Airflow (MAF) and Intake Air Temperature (IAT) sensors are combined into a single unit and located between the air filter housing and the intake manifold. ECM uses input signals from the MAF/IAT sensor unit to calculate volume of air flowing into the engine.

The Intake Air Temperature (IAT) sensor uses a thermistor with a Negative Temperature Coefficient (NTC). As intake air temperature increases, IAT sensor resistance and output voltage decreases. If there is an IAT sensor failure, ECM will substitute a value of 113°F (45°C) for intake air temperature.

IAT sensor can fail or supply an incorrect signal in the following ways

1. Adaptive fueling is disabled.
2. Idle speed adaptation is disabled.
3. Catalyst monitoring affected due to exhaust temperature model.
4. Idle speed actuator test is disabled.
5. Warm up ignition angle is affected.
6. Condenser fan hot restart is inhibited.

IAT sensor can fail or supply an incorrect signal because of the following

1. Open in sensor harness.
2. Short to battery voltage in sensor harness.
3. Short to ground in sensor harness.
4. Increased sensor resistance.
5. Contaminated or damaged sensor element.

1. If DTC P0111 is set, there is an Intake Air Temperature (IAT) sensor circuit range or performance problem.
2. If DTC P0112 is set, IAT sensor signal is less than minimum threshold, after expected time for exhaust to warm up. The IAT sensor signal will be less than the minimum threshold if the engine has been operating for more than 180 seconds, idle speed control has not been operational for more than 10 seconds, there is no active fuel cut off and the IAT sensor signal indicated is less than -31°F (-35°C) for more than 200 mS.
3. If DTC P0113 is set, IAT sensor signal is more than maximum threshold. The IAT sensor signal will be more than the maximum threshold if the ECM is energized (engine does not need to be operating) and the signal indicated is more than 284°F (140°C) for more than 200 mS.

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). (Scheme 9) See appropriate wiring diagram in appropriate wiring diagram in 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. When repairs are complete, go to step 5.
2. 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 C0636, 52-pin connector terminal No. 9. Perform repairs as necessary. When repairs are complete, go to step 5.
3. 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 will decrease as intake air temperature increases. If voltage is as specified, go to next step. If voltage is not as specified, replace IAT sensor and retest. When repairs are complete, go to step 5.
4. 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 decrease and intake air temperature increases. 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. When repairs are complete, go to next step.
5. When DTC P0111, P0112 or P0113 repairs are completed, perform «REPAIR CONFIRMATION DRIVE CYCLE "B"»(/land-rover/discovery/l318-1998-2002/remont/testing-diagnostics/#engine-controls-self-diagnostics-with-codes__repair-confirmation-drive-cycle-b).

ECT sensor is located at top front of engine, next to upper coolant outlet pipe. ECT sensor have a Negative Temperature Coefficient (NTC) thermistor. As coolant temperature increases, sensor thermistor resistance decreases, as coolant temperature decreases, sensor thermistor resistance increases. ECM receives a 0.0-5.0 volt analog signal which is used to control fuel injector ON time during cold starting and warm-up (a richer mixture at low coolant temperatures and a leaner mixture at high coolant temperatures).

On Discovery Series II, ECT sensor uses one thermistor and a 4-pin connector with 2 wires. (Scheme 10) ECM supplies the instrument cluster with a Pulse Width Modulated (PWM) coolant temperature signal temperature gauge operation. ECM provides ECT sensor with a 5-volt reference via ECM 52-pin connector C0636 terminal No. 22 (Green wire). ECM provides ECT sensor ground via ECM 52-pin connector C0636 terminal No. 21 (Red/Black wire). (Scheme 7)and (Scheme 8).

On Range Rover, ECT sensor uses 2 thermistors and a 4-pin connector with 4 wires. (Scheme 10) ECM uses ECT sensor thermistor input signals from 2 wires to control fuel injector ON time. The other ECM sensor thermistor analog signals from the other 2 wires are used by the Body Control Module (BECM) to control engine temperature warning lamp operation on instrument cluster. ECM provides ECT sensor with a 5-volt reference via ECM 52-pin connector C0636 terminal No. 22 (Green/Blue wire). ECM provides ECT sensor ground via ECM 52-pin connector C0636 terminal No. 21 (Red/Black wire). (Scheme 7)and (Scheme 8).

On all models equipped with Secondary Air Injection (SAI), ECT sensor signal is monitored by ECM at engine start, to determine if the engine is cold enough to warrant SAI operation. ECT sensor is then monitored to switch off the SAI when required engine coolant temperature has been attained.

If there is an ECT sensor failure the ECM uses a changing default value during warm up based on Inlet Air Temperature (IAT) sensor signal. When strategy default value is 140°F (60°C), ECM implements a fixed ECT sensor default value of 185°F (85°C). It will also illuminate the MIL. An ECT sensor failure may result in a fast idle condition on initial start-up until normal operating temperature value is reached.

If there is an ECT sensor signal failure any of the following symptoms may be observed

1. Poor cold or warm/hot starting and driveability.
2. MIL will be illuminated.
3. Instrument cluster temperature warning lamp will be illuminated.
4. Temperature gauge reads excessively cold or hot.
5. Cooling fan will not operate.
6. Secondary Air Injection (SAI) pump will operate at engine start up even when engine is hot.

ECT sensor can fail or supply incorrect signal in the following ways

1. ECT sensor open circuit.
2. ECT sensor circuit short to battery voltage.
3. ECT sensor circuit short to ground.
4. Incorrect mechanical fitting.
5. An ECT sensor signal fixed at more than 104°F (40°C) will not be detected.
6. An ECT sensor signal fixed at less than 104°F (40°C) will not be detected.

1. If DTC P0115 is set, there is an Engine Coolant Temperature (ECT) sensor circuit malfunction.
2. If DTC P0116 is set, there is an Engine Coolant Temperature (ECT) circuit/range performance problem. The ECT sensor signal is within limits, but is inaccurate (ECT sensor signal indicates a coolant temperature that is less than 104°F (40°C) and engine is operating). The difference between the ECT sensor signaled temperature and the ECM's expected temperature (based on other sensors) is too much for more than 2.53 seconds.
3. If DTC P0117 is set, there is an Engine Coolant Temperature (ECT) sensor low input signal to ECM. The problem could be an open circuit or short to battery voltage.
4. If DTC P0118 is set, Engine Coolant Temperature (ECT) sensor high input signal to ECM. The problem could be caused by a short circuit to ground.

1. Check for a contaminated sensor, poor connections, loose terminals, and open or shorted wires. See appropriate wiring diagram in WIRING DIAGRAMS article. (Scheme 7), (Scheme 8) and (Scheme 10). If no problems are found, go to next step. Perform repairs as necessary. When repairs are complete, go to step 3.
2. Using a thermometer, monitor engine coolant temperature at radiator. Start engine and allow to idle. Backprobe between ECM 52-pin connector C0636 terminals No. 21 (Red/Black wire) and No. 22 (Green wire on Discovery Series II; Green/Blue wire on Range Rover). Compare expected ECT sensor voltage output with monitored engine coolant temperature. See «ENGINE COOLANT TEMPERATURE SENSOR VALUES»(/land-rover/discovery/l318-1998-2002/remont/testing-diagnostics/#engine-controls-self-diagnostics-with-codes) table. Replace ECT sensor of output voltage does not agree with monitored engine coolant temperature. When repairs are complete go to next step.
3. When DTC P0115-P0118 repairs are completed, perform «REPAIR CONFIRMATION DRIVE CYCLE "B"»(/land-rover/discovery/l318-1998-2002/remont/testing-diagnostics/#engine-controls-self-diagnostics-with-codes__repair-confirmation-drive-cycle-b).

ENGINE COOLANT TEMPERATURE SENSOR VALUES

Scheme 10

DTC P0120, P0122, P0123: THROTTLE POSITION (TP) SENSOR CIRCUIT

Note. DTC P0101 will set based on compared signals from the Mass Airflow (MAF)/Intake Air Temperature (IAT) sensors and the Throttle Position (TP) sensor. DTC P0101 is a load monitoring DTC based on an unexpected throttle position ratio to airflow. DTC P0101 will set if there is a mass or volume airflow circuit range or performance problem.

TP sensor is located on the rear of the throttle body assembly in the engine compartment. TP sensor signal informs ECM of actual throttle position and rate of change in throttle position. ECM compares TP sensor output with Mass Airflow (MAF) sensor output. If values from these two sensors do not agree and fuel injection feedback indicates correct air/fuel mixture, ECM assumes MAF sensor is correct and TP sensor has failed. During deceleration when the ECM receives a closed throttle position signal from the TP sensor the ECM closes fuel injectors for as long as the throttle is closed.

The TP sensor signal is also used by the Electronic Automatic Transmission (EAT) ECU to determine correct points for gear shifts and acceleration kickdown. On Discovery Series II, ECM also supplies the Self-Leveling and ABS (SLABS) ECU and the Active Cornering Enhancement (ACE) ECU with TP sensor information as a PWM signal. On all models, the EAT ECU not seeing a TP signal will cause poor gear change quality, loss of kickdown or EAT ECU to select default transmission control.

If there is a TP sensor signal failure the ECM uses a default value derived from engine load and speed. A TP sensor failure may result in the following symptoms

1. Poor engine performance.
2. Delayed throttle response.
3. Emission control failure.
4. Closed loop idle speed control inoperative.
5. Automatic gearbox kickdown inoperative.
6. Incorrect altitude adaptation.
7. MIL illuminated.

TP sensor can fail or supply incorrect signal in the following ways

1. TP sensor open circuit.
2. Short to battery voltage or ground.
3. Signal out of parameters.
4. Restriction in air inlet or blocked air filter (load monitoring, ratio of the TP sensor to MAF sensor).
5. Vacuum leak.

1. If DTC P0101 is set, there is a mass or volume airflow circuit range or performance problem. DTC P0101 is a load monitoring DTC based on an unexpected throttle position ratio to mass of airflow. DTC P0101 will set if the calculated throttle angle is outside limits when engine speed is between 800-4000 RPM, engine load is between 2.0-6.5 and engine coolant temperature is more than 14°F (-10°C).
2. If DTC P0120 is set, there is TP sensor/pedal position switch "A" circuit malfunction.
3. If DTC P0122 is set, there is TP sensor/pedal position switch "A" circuit low input signal. DTC will set when TP sensor signal is less than minimum threshold when engine speed is more than 400 RPM for longer than 2.0 seconds and the signal is less than 2.0 percent for longer than 50 mS.
4. If DTC P0123 is set, there is TP sensor/pedal position switch "A" circuit high input signal. DTC will set when TP sensor signal is more than maximum threshold value when engine speed is more than 400 RPM for longer than 2.0 seconds and the signal is more than 96.0 percent for longer than 50 mS.

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 appropriate wiring diagram in WIRING DIAGRAMS article. (Scheme 7), (Scheme 8) and (Scheme 11). If no problems are found, go to next step. Perform repairs as necessary. When repairs are complete, go to step 3.
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. If voltage is as specified and changes smoothly, go to next step. If voltage is not as specified, replace TP sensor. When repairs are complete, go to next step.
3. When DTC P0101, P0120, P0122 or P0123 repairs are completed, perform «REPAIR CONFIRMATION DRIVE CYCLE "A"»(/land-rover/discovery/l318-1998-2002/remont/testing-diagnostics/#engine-controls-self-diagnostics-with-codes__repair-confirmation-drive-cycle-a).

THROTTLE POSITION SENSOR SIGNAL VOLTAGE

Scheme 11

There are 4 Heated Oxygen Sensors (HO2S) located in the exhaust system. Front HO2S (bank 1, sensor 1) is located in front of the left side catalytic converter. Rear HO2S (bank 1, sensor 2) is located after the left side catalytic converter. Front HO2S (bank 2, sensor 1) is located in front of the right side catalytic converter. Rear HO2S (bank 2, sensor 2) is located after the right side catalytic converter. Rear HO2S measure oxygen content after catalytic converters to monitor operating efficiency of converters.

Each HO2S is electrically heated to ensure sensor achieves operating temperature as quickly as possible after start-up. ECM energizes HO2S heater using a Pulse Width Modulation (PWM) signal which starts low and increases within 30 seconds to desired heater temperature. Primary HO2S heaters are wired in parallel and secondary HO2S heaters are wired in parallel for synchronous ECM control of each heater pair.

HO2S operating temperature is approximately 662°F (350°C). To achieve and maintain this temperature there is a heating element incorporated in HO2S which is controlled by a PWM signal from the ECM. The HO2S heating elements are activated immediately after engine start or during low engine load conditions when exhaust gas temperature is insufficient to maintain the required HO2S operating temperature. If the heater fails, the ECM will not allow closed loop fueling to be implemented until the sensor has achieved the required operating temperature. This value equates to an HO2S output signal of 450-500 mV. A richer mixture will increase HO2S output voltage towards 1000 mV. A leaner mixture decreases HO2S output voltage towards 100 mV. From cold start, ECM runs an open loop fueling strategy. ECM keeps this strategy in place until the HO2S is at a normal operating temperature. At this point the ECM starts to receive HO2S information and it can then switch into closed loop fueling as part of its adaptive strategy. The maximum operating temperature of the HO2S tip is 1706°F (930°C), temperatures greater than this will damage the sensor.

In the event of a HO2S signal failure any of the following symptoms may be observed

1. Default to open loop fueling on defective bank.
2. ECM will eventually default into open loop fueling.
3. High CO reading.
4. Excessive emissions.
5. Strong hydrogen sulfide smell like a strong smell of rotten eggs until the ECM defaults to open loop fueling.
6. MIL will be illuminated.

HO2S can fail in the following ways or supply incorrect signal

1. HO2S sensor open circuit.
2. Short circuit to battery voltage.
3. Short circuit to ground.
4. Sensor disconnected.
5. Stoichiometric ratio outside the correct operating band.
6. HO2S contamination from leaded fuel or other source.
7. Air leak into the exhaust system.
8. Wiring harness damage.
9. Sensors installed incorrectly or cross wired.

Note. Front and rear HO2S sensors are not interchangeable even though they can be mounted in reversed positions. The harness connections are different: Orange in front and Gray in rear. Connector signal terminals are gold plated and heater supply terminals are tin plated. Interchanging terminals will cause contamination and adversely affect system performance.

If front HO2S wiring is crossed over (LH bank to RH bank), engine will run normally after initial start up, but performance will become progressively worse as sensors go towards maximum rich for one bank of cylinders and maximum lean for the other. If front HO2S wiring is switched left for right, vehicle will operate properly until sensors reach operating temperature. ECM will then cause one bank of cylinders to run very rich and the other bank to run very lean. This will cause engine to misfire, idle rough and emit black smoke, with possible catalytic converter damage.

1. If DTC P0130, P0136, P0150 or P0156 is set, there is a circuit malfunction, caused by the stoichiometric ratio of suspect sensor is outside normal operating range.
2. If DTC P0131, P0137, P0151 or P0157 is set, the sensor signal voltage is less than expected, caused by a sensor circuit short to ground.
3. If DTC P0132, P0138, P0152 or P0158 is set, the sensor signal voltage is more than expected, caused by a sensor circuit short to battery voltage.
4. If DTC P0133 or P0153 is set, the front sensor is aged, indicated by a slow responding sensor signal that is either too long or too short.
5. If DTC P0134, P0140, P0154 or P0160 is set, no sensor activity is detected, caused by an open circuit.
6. If DTC P0135, P0141, P0155 or P0161 is set, there is a sensor heater circuit malfunction, caused by an open or short circuit.
7. If DTC P1129 is set, the front sensor connectors have been swapped side to side.
8. If DTC P1170 or P1173 is set, there is a downstream fuel trim malfunction caused by a front sensor that is aged, indicated by a rear HO2S adaptation that is too lean or too rich.

1. Check for contaminated sensor, poor connections, loose terminals, and open or shorted wires. Ensure wiring to front sensors is not crossed. See appropriate wiring diagram in WIRING DIAGRAMS article. (Scheme 7), (Scheme 8), (Scheme 12) and (Scheme 13). Perform repairs as necessary. When repairs are completed, go to step 3.
2. Start engine and allow to operate at normal operating temperature. Backprobe specified ECM C0635 connector terminals for suspect HO2S and check signal values. HO2S voltage is difficult to measure using a DVOM, HO2S output can be monitored using a Land Rover TestBook, an OBD-II scan tool or an oscilloscope. A rich mixture should read 500-1000 mV, a lean mixture should read 100-500 mV, and the reading should switch from rich to lean and back. The ECM open loop default voltage is 450 mV, this is used to set the air/fuel ratio until the HO2S reaches operating temperature. Perform repairs as necessary. When repairs are completed, go to next step.
3. When HO2S related DTC repairs are completed, perform specified REPAIR CONFIRMATION DRIVE CYCLE. See DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION (BOSCH) table in SELF-DIAGNOSTICS - INTRODUCTION article.

IDENTIFYING ECM C0635 CONNECTOR HO2S TERMINALS

Scheme 12

Scheme 13

During adaptive fueling conditions, ECM uses information from HO2S to correct fuel quantity to keep air/fuel ratio as close to the stoichiometric ideal as possible. Closed loop fueling is used as part of ECM fueling strategy. The operation of the three-way catalytic converter relies on ECM being able to optimize the air/fuel mixture, switching between rich and lean either side of the stoichiometric ideal.

Fuel trim refers to feedback compensation value compared against basic injection time. Fuel trim includes short-term and long-term fuel trim.

1. If DTC P0170 is set, there is a fuel trim malfunction at Bank 1.
2. If DTC P0171 is set, system is too lean at Bank 1. There is an additive or multiplication injector adaptive fueling malfunction indicated by an exceeded lean limit.
3. If DTCP0172 is set, system is too rich at Bank 1. There is an additive or multiplication injector adaptive fueling malfunction indicated by an exceeded rich limit.
4. If DTC P0173 is set, there is a fuel trim malfunction at Bank 2.
5. If DTC P0174 is set, system is too lean at Bank 2. There is an additive or multiplication injector adaptive fueling malfunction indicated by an exceeded lean limit.
6. If DTC P0175 is set, system too rich at Bank 2. There is an additive or multiplication injector adaptive fueling malfunction indicated by an exceeded rich limit.
7. If DTC P1171 is set, system is too rich at Bank 1. There is an additive injector adaptive fueling malfunction indicated by an exceeded rich limit.
8. If DTC P1172 is set, system is too lean at Bank 1. There is an additive injector adaptive fueling malfunction indicated by an exceeded lean limit.
9. If DTC P1174 is set, system is too rich at Bank 2. There is an additive injector adaptive fueling malfunction indicated by an exceeded rich limit.
10. If DTC P1175 is set, system is too lean at Bank 2. There is an additive injector adaptive fueling malfunction indicated by an exceeded lean limit.

Check for an intake air leak between MAF sensor and throttle body. Ensure fuel pressure is correct. Check for a clogged or leaking fuel injector. Ensure MAF, ECT and HO2S sensors are operating properly. Check exhaust system for leaks. Perform repairs as necessary. When DTC P0170-P0175 repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "C" .

Multiport Sequential Fuel Injection (SFI) system uses one fuel injector per cylinder. Fuel injectors are fitted between pressurized fuel rail and intake manifold. Each injector contains a solenoid controlled by ECM. When solenoid is energized, a plunger is pulled off its seat and allows pressurized fuel to spray into the intake manifold. Fuel injector total failure or a leak that causes a rich mixture will cause a misfire in affected cylinder.

On Discovery Series II, the fuel injectors are supplied with battery voltage through the main relay via fuse No. 1 (30-amp) located in engine compartment fuse box. On Range Rover, the fuel injectors are supplied with battery voltage through the main relay via fuse No. 37 (30-amp) located in engine compartment fuse box. On all models, fuel injector operation is controlled by the ECM through the ground path of each fuel injector. This facility allows the ECM to control the fuel injectors so that sequential fuel injection can take place.

Specific fuel injector failures will generate a specific DTC for suspect injector that are stored in the ECM as follows

Injector No. 1

1. DTC P0201 will set because of an open circuit.
2. DTC P0261 will set because of a short circuit to ground.
3. DTC P0262 will set because of a short to battery voltage.

Injector No. 2

1. DTC P0202 will set because of an open circuit.
2. DTC P0264 will set because of a short circuit to ground.
3. DTC P0265 will set because of a short to battery voltage.

Injector No. 3

1. DTC P0203 will set because of an open circuit.
2. DTC P0267 will set because of a short circuit to ground.
3. DTC P0268 will set because of a short to battery voltage.

Injector No. 4

1. DTC P0204 will set because of an open circuit.
2. DTC P0270 will set because of a short circuit to ground.
3. DTC P0271 will set because of a short to battery voltage.

Injector No. 5

1. DTC P0205 will set because of an open circuit.
2. DTC P0273 will set because of a short circuit to ground.
3. DTC P0274 will set because of a short to battery voltage.

Injector No. 6

1. DTC P0206 will set because of an open circuit.
2. DTC P0276 will set because of a short circuit to ground.
3. DTC P0277 will set because of a short to battery voltage.

Injector No. 7

1. DTC P0207 will set because of an open circuit.
2. DTC P0279 will set because of a short circuit to ground.
3. DTC P0280 will set because of a short to battery voltage.

Injector No. 8

1. DTC P0208 will set because of an open circuit.
2. DTC P0282 will set because of a short circuit to ground.
3. DTC P0283 will set because of a short to battery voltage.

If a fuel injector should fail, the following symptoms may be observed

1. Rough running.
2. Difficult starting.
3. Engine misfire.
4. Possible catalyst damage.
5. High emissions.
6. Fueling and idle speed control adaptations disabled.

A fuel injector failure is likely to occur for the following reasons

1. Actuator open circuit.
2. Short circuit to battery voltage or ground.
3. Blocked or restricted fuel injector.
4. Low fuel pressure.

Using a stethoscope, listen for clicking sounds from each injector with engine at idle. Check resistance between injector terminals. Injector resistance should be 13.8-15.2 ohms at 68°F (20°C). Check for poor connections, loose terminals, and open or shorted wires. See WIRING DIAGRAMS article. Check for low fuel pressure and/or a blocked, leaking or dripping injectors. Perform repairs as necessary. When fuel injector DTC repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "A" .

The flywheel and reluctor ring are divided into four 90-degree segments. The ECM misfire detection system uses information from the Crankshaft Position (CKP) sensor to determine crankshaft speed and position. If a misfire occurs, there will be an instantaneous decrease in engine speed. The ECM is able to compare the length of time each 90-degree segment takes and is therefore able to pinpoint the source of the misfire.

The ECM performs misfire detection as part of OBD system using the following

1. Crankshaft Position (CKP) Sensor.
2. Calculation of engine roughness.
3. Detection of excess emissions misfire.
4. Detection of catalyst damaging misfire.

If the ECM has detected a misfire in one or more cylinders one of the following DTCs may be set

1. If DTC P0300 is set, a random misfire has been detected in more than one cylinder. MIL will be illuminated.
2. If DTC P0301-P0308 is set, a misfire has been detected in a specific cylinder. MIL will be illuminated.
3. If DTC P1300 is set, a misfire has been detected sufficient to cause catalyst damage on more than one cylinder. MIL will be illuminated.
4. If DTC P1319 is set, a misfire has been detected with a low fuel level in fuel tank. MIL will not be illuminated.
5. If DTC P1301-P1308 is set, a catalyst damaging level of misfire has been detected on specific cylinder.

1. Ensure ECM misfire detection system is properly calibrated for the fluctuations between CKP sensor and the reluctor tooth positions. ECM carries out flywheel and reluctor ring adaptations at various engine speed ranges and can be monitored by TestBook. See «ECM MISFIRE DETECTION ENGINE SPEED»(/land-rover/discovery/l318-1998-2002/remont/testing-diagnostics/#engine-controls-self-diagnostics-with-codes) table. ECM MISFIRE DETECTION ENGINE SPEED Speed Range Engine Speed 1 1800-3000 RPM 2 3000-3800 RPM 3 3800-4600 RPM 4 4600-5400 RPM
2. Install Land Rover TestBook and monitor ECM misfire detection system calibration and engine speed. Start engine and allow to idle at normal operating temperature. Select 2nd gear and slowly accelerate until engine revolution limiter is activated. Slowly release throttle to allow engine to decelerate through each speed range. Repeat process as necessary until calibration is complete.
3. Check for fuel contamination, leaking or blocked fuel injector, faulty spark plugs or wires, faulty coil, low fuel pressure, low cylinder compression, or broken valve spring. When DTC repairs are completed, perform «REPAIR CONFIRMATION DRIVE CYCLE "C"»(/land-rover/discovery/l318-1998-2002/remont/testing-diagnostics/#engine-controls-self-diagnostics-with-codes__repair-confirmation-drive-cycle-c) .

KS "A" is located on left side of engine block between cylinders No. 3 and No. 5, and KS "B" is located on right side of engine between cylinders No. 2 and No. 4. KS contains a piezoelectric ceramic element which produces a voltage proportional to engine vibration. ECM uses KS, Camshaft Position (CMP) sensor and Crankshaft Position (CKP) sensor signals to verify engine knock based on positions of cylinders. If CMP sensor fails, ECM will disable knock control. If knock control is disabled, ECM will default to a safe ignition map.

If a knock sensor should fail, the following symptoms may be observed

1. Possible rough running.
2. Reduction in engine performance.

Noise induced on the battery supply line could be misinterpreted as a knock signal and cause a maximum knock fault. A maximum fault could be caused by a short circuit to the battery supply or in the case of extreme mechanical engine noise/piston slap. A minimum fault is usually due to an open circuit.

A knock sensor failure is likely to occur for the following reasons

1. An open sensor circuit.
2. A short circuit to battery voltage or ground.
3. A malfunctioning KS sensor.
4. An incorrectly installed KS sensor.

When the ECM performs diagnostic checks to confirm correct KS operation the engine must be operating, the engine coolant temperature must be more than 140°F (60°C), and the number of camshaft revolutions since engine start must be more than 50. For a KS DTC to set the KS signal profile must be less than or more than the threshold value at a specific engine speed or the error counter must be greater than the threshold value at a given engine speed.

If a KS should fail, the following DTCs may be set

1. If DTC P0327 is set, the left bank KS signal is less than the threshold value determined by the ECM when engine speed is more than 2200 RPM.
2. If DTC P0328 is set, the left bank KS signal greater than the threshold value determined by the ECM when engine speed is more than 2200 RPM.
3. If DTC P0332 is set, the right bank KS signal is less than the threshold value determined by the ECM when engine speed is more than 2200 RPM.
4. If DTC P0333 is set, the right bank KS signal is greater than the threshold value determined by the ECM when engine speed is more than 2200 RPM.

Check for poor connections, loose terminals, and open or shorted wires. See appropriate wiring diagram in WIRING DIAGRAMS article. When DTC repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "B" .

CKP sensor is located on the left side of flywheel housing, below cylinder No. 7. A reluctor ring mounted to flywheel is used to generate a the CKP signal. CKP sensor provides ECM with information indicating that engine is turning, engine speed and crankshaft position during engine cycle. ECM controls fuel injection and coil firing based on signal from CKP sensor. Engine overspeed protection is set at 5500 RPM and is based on CKP sensor signal.

The tip of the CKP sensor protrudes through an aperture in the engine block rear flange, adjacent to the outer circumference of the flywheel. A 60-tooth reluctor ring is mounted to the flywheel which provides the reference signal to the CKP sensor. The output voltage varies in proportion to engine speed. The reluctor ring has a set tooth pattern, 60 teeth are spaced at 6 degrees intervals and are 3 degrees wide. Two teeth are removed to provide a reference mark at 60° BTDC for No. 1 cylinder. There is no back up strategy or limp home mode if sensor fails, the engine will stop or will not start.

There is no default strategy for the CKP sensor. In the event of a CKP sensor signal failure any of the following symptoms may be observed

1. Engine cranks but fails to start.
2. MIL remains on at all times.
3. Engine misfires (CKP sensor incorrectly fitted).
4. Engine runs roughly or even stalls (CKP sensor incorrectly fitted).
5. Tachometer fails to operate.

If a CKP sensor should fail, the following DTCs may be set

1. If DTC P0335 is set, the reference mark is outside search window when engine speed is more than 500 RPM for more than 2 revolutions.
2. If DTC P0336 is set, the incorrect number of teeth have been detected plus or minus one tooth between reference marks when engine speed is more than 500 RPM.

It is vital that the correct air gap is maintained, if the air gap becomes too wide the CKP signal becomes too weak, causing possible engine misfires to occur. The correct air gap between the tip of CKP sensor and passing reluctor ring teeth is set using the correct spacer. A 0.55" (14 mm) spacer is used on vehicles with M/T and a 0.70" (18 mm) spacer is used on vehicles with A/T. CKP sensor can fail the following ways or supply incorrect signal

1. CKP sensor assembly loose.
2. An incorrect spacer has been installed.
3. There is a sensor open or short circuit.
4. Incorrect sensor installation and integrity.
5. Water contaminated sensor connector.
6. ECM unable to detect software reference point.
7. Sensor pin and/or reluctor ring contamination by ferrous metal or other debris.

Check for poor connections, loose terminals, and open or shorted wires. (Scheme 11) See appropriate wiring diagram in WIRING DIAGRAMS article. Ensure CKP sensor pin is not bent, that reluctor ring runs true and that there are no teeth missing, bent or chipped. Ensure CKP sensor is correctly installed and that no water or coolant has entered sensor connector. Sensor resistance should be approximately 1235-1365 ohms. When DTC P0335 or P0336 repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "A".

DTC P0340: CAMSHAFT POSITION (CMP) SENSOR MALFUNCTION

Note. CMP sensor circuit fault or signal timing different from CKP sensor signal. It is physically possible to install the camshaft gear wheel used on a vehicle equipped with a GEMS ignition system to a vehicle equipped with a Bosch Motronic ignition system, and vice-versa. However, because the GEMS and Motronic systems are incompatible, an incorrect camshaft signal will be received by the ECM and DTC P0340 will set.

CMP sensor is a Hall Effect sensor located in the engine front cover, above and behind the crankshaft pulley. CMP sensor produces 4 pulses for every 2 revolutions of the engine (one pulse is slightly longer than the others). CMP sensor is positioned close to the camshaft gear wheel, the gear wheel has 4 slots machined at 90 degree intervals. This allows ECM to recognize 4 individual cylinders every camshaft revolution or all 8 cylinders every crankshaft revolution. CMP sensor Hall effect works as a magnetic switch. It switches battery voltage on or off depending on the position of the camshaft gear wheel in relationship to the sensor. The ECM uses this signal for cylinder recognition to control sequential fuel injection, engine knock and diagnostic purposes.

If CMP sensor fails, default strategy is to continue normal ignition timing. Fuel injection timing will default to bank control based on top dead center timing. Injection timing will either be correct or one revolution out of synchronization. Individual cylinder knock control will be disabled and misfire identification may be incorrect. There may not be a driveability problem with a fault being indicated by illumination of the MIL.

The CKP sensor failure must be detected for more than 100 cam pulses (25 engine revolutions) when engine speed is greater than 500 RPM. If there is a CMP sensor signal failure any of the following symptoms may be observed

1. Ignition timing reverts to default values from ECM memory.
2. Loss of cylinder correction and/or active knock control.
3. Loss of active knock control diagnostics.
4. Loss of cylinder identification for misfire diagnostics.
5. Loss of quick synchronization of crankshaft and camshaft for cranking/start up.
6. Fuel injection could be 360 degrees out of phase.
7. Front HO2S sensor aging period diagnostic disabled.

CMP sensor battery voltage is supplied to connector terminal No. 3 (Brown/Pink wire). On Discovery Series II, battery voltage is supplied through the main relay via fuse No. 2 (15-amp) located in engine compartment fuse box. On Range Rover, CMP sensor is supplied with battery voltage through the main relay via fuse No. 26 (20-amp) located in engine compartment fuse box. On all models, ground is supplied to CMP sensor connector terminal No. 1 (Black wire). CMP sensor signal output to ECM 52-pin connector C0636 terminal No. 20 is from CMP sensor connector terminal No. 2 (Gray/Blue wire). (Scheme 14)

CMP sensor can fail or supply an incorrect signal in the following ways

1. An open sensor circuit.
2. Short circuit to battery voltage or ground.
3. Incorrectly installation.
4. Excessive CMP sensor to camshaft gear wheel gap or camshaft end-float.
5. Camshaft and crankshaft misalignment.
6. Speed signal correlation with CKP sensor signal.
7. Camshaft gear wheel magnetized or residual magnetism.

Check for poor connections, loose terminals, and open or shorted wires. See appropriate wiring diagram in WIRING DIAGRAMS article. (Scheme 7), (Scheme 8) and (Scheme 14). Unsure CMP sensor is correctly mounted and that sensor connector is clean and tight. When DTC P0340 repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "A".

Scheme 14

Secondary Air Injection (SAI) system is used to supply additional air to the exhaust system, just behind the exhaust valves. This additional air is used to decrease amount time required for catalytic converters to reach normal operating temperature. SAI system includes a SAI pump, SAI vacuum solenoid valve, 2 SAI control valves (1 for each bank of cylinders), SAI pump relay, vacuum reservoir, vacuum harness and pipes. (Scheme 15)or (Scheme 16).

When engine is started the ECM checks engine coolant temperature. If engine coolant temperature is less than 131°F (55°C), ECM will activate SAI pump. SAI pump will operate for approximately 95 seconds when engine coolant temperature is 46°F (8°C) and approximately 30 seconds when engine coolant temperature is 131°F (55°C). ECM can cancel SAI pump operation if engine speed or load is excessive.

When ECM energizes the SAI pump, the ECM energizes the SAI vacuum solenoid valve, which opens the SAI vacuum valve. When vacuum valve opens vacuum from the reservoir is applied to the vacuum operated SAI control valves on each side of the engine. When vacuum is applied the SAI control valves open simultaneously and allow air from SAI pump through to the exhaust ports. Secondary air is injected into the inner most exhaust ports on each bank.

When ECM breaks the ground circuit to de-energize SAI vacuum solenoid valve, the vacuum supply to the SAI control valves is cut off and the valves close to prevent further air being injected into the exhaust manifold. At the same time as the SAI vacuum solenoid valve is closed, the ECM opens the ground circuit to the SAI pump relay, to stop the SAI pump. A vacuum reservoir is included in the vacuum line between the intake manifold and the SAI vacuum solenoid valve. This prevents changes in vacuum pressure from the intake manifold being passed on to cause fluctuations of the secondary air injection solenoid valve. The vacuum reservoir contains a one way valve and ensures a constant vacuum is available for the SAI vacuum solenoid valve operation. This is particularly important when the vehicle is at high altitude.

Note. SAI solenoid valve harness 2-pin connector is Gray. Do not confuse with EVAP system purge control valve harness 2-pin connector which is Black.

Battery voltage for SAI air pump operation is supplied from the SAI air pump relay and fusible link No. 2 (50-amp) which are located in the engine compartment fuse/relay box. Operation of SAI pump relay is controlled by ECM through ground circuit. ECM energizes the SAI vacuum solenoid valve at the same time that the SAI air pump is energized. On Discovery Series II, battery voltage for SAI vacuum solenoid valve operation is supplied from Main relay and fuse No. 2 (15-amp) located in the engine compartment fuse/relay box. On Range Rover, battery voltage for SAI vacuum solenoid valve operation is supplied from Main relay and fuse No. 26 (20-amp) located in the engine compartment fuse/relay box. On all models, the ground connection is via the ECM which controls the SAI vacuum solenoid valve operation.

If there a SAI system failure, the following DTCs may be set

1. If DTC P0412 is set, there is a SAI vacuum solenoid valve power supply malfunction caused by a short to battery voltage.
2. If DTC P0413 is set, SAI vacuum solenoid valve is not connected caused by an open circuit.
3. If DTC P0414 is set, there is a SAI vacuum solenoid valve short circuit to ground.
4. If DTC P0418 is set, there is a SAI air pump power supply malfunction. Possible causes are a SAI air pump relay malfunction, SAI air pump or relay not connected, an open circuit or damaged harness.

Scheme 15

Scheme 16

Check for poor connections, loose terminals, and open or shorted wires. See appropriate wiring diagram in WIRING DIAGRAMS article. (Scheme 7), (Scheme 8) and (Scheme 17). When DTC P0340 repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "A".

Scheme 17

There are 2 Heated Oxygen Sensors (HO2S) mounted at rear of each catalytic converter. The rear HO2S are used to monitor catalyst efficiency. If the left bank catalyst efficiency has deteriorated DTC P0420 will set. If the right side catalyst efficiency has deteriorated DTC P0430 will set. In either case the MIL will be illuminated.

Visually inspect intake and exhaust systems for damage or leaks. Ensure front HO2S and MAF sensor are operating properly. Check for poor connections, loose terminals, and open or shorted wires. See appropriate wiring diagram in WIRING DIAGRAMS article. Check for other DTCs. When DTC P0420 and P0430 repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "C" .

When the ECM grounds EVAP purge valve, the valve opens to allow fuel vapors stored in the EVAP canister to be purged to the engine intake manifold. If the EVAP purge valve malfunctions or sticks in the open or closed position, the EVAP system will cease to function. A DTC will be set and the MIL will be illuminated if the valve status is unchanged for 45 seconds after engine has been running for 15 minutes. The ECM does not have a default operation available. If the purge valve is stuck open, a rich air fuel mixture is likely to result, causing engine misfire and fueling adaptations to change.

ECM must control EVAP system purging to maintain driveability and effective emission control. An unexpected one percent concentration of fuel vapor from the EVAP canister added to intake air can shift the air fuel ratio by as much as 20 percent. ECM must purge fuel vapor from EVAP canister at regular intervals to prevent excessive build-up of fuel pressure in system and possible vapor leaks. Canister purging is cycled with fueling adaptation because both cannot be active at the same time. ECM alters purge valve PWM signal to control purging rate of the EVAP canister to maintain optimum stoichiometric air fuel mixture for the engine.

An EVAP purge valve malfunction could be caused by the following

1. Sticking EVAP purge valve.
2. EVAP purge valve blocked.
3. EVAP purge valve connector or harness wiring open or short circuit.
4. EVAP purge valve stuck open.

Possible symptoms associated with purge valve or associated pipe failure are

1. Engine may stall on return to idle if purge valve is stuck open.
2. Poor idle quality if the purge valve is stuck open.
3. Fueling adaptations forced excessively lean if the EVAP canister is clear and the purge valve is stuck open.
4. Fueling adaptations forced excessively rich if the EVAP canister is saturated and the purge valve is stuck open.
5. Saturation of the EVAP canister if the purge valve is stuck closed.

If the purge valve malfunctions, the following DTCs may be set

1. If DTC P0440 is set, EVAP purge valve not sealing properly.
2. If DTC P0441 is set, an incorrect purge flow has been detected.
3. If DTC P0443 is set, there is an EVAP purge valve short circuit to battery voltage.
4. If DTC P0444 is set, there is an EVAP purge valve open circuit.
5. If DTC P0445 is set, there is an EVAP purge valve short circuit to ground.

Note. EVAP system purge control valve harness 2-pin connector is Black. Do not confuse with SAI solenoid valve harness 2-pin connector is which Gray.

Check for broken or leaking hoses and poor hose connections. Ensure SAI solenoid valve is mounted correctly with directional arrow pointing towards intake air plenum chamber. Check for poor electrical connections, loose terminals, and open or shorted wires. See appropriate wiring diagram in WIRING DIAGRAMS article. (Scheme 7), (Scheme 8) and (Scheme 17). When DTC P0440 repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "E". When DTC P0443-P0445 repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "A".

EVAP system includes a fuel pressure sensor and a Canister Vent Solenoid (CVS) valve. The system is capable of detecting holes in the fuel system down to 0.04" (1 mm).

ECM carries out test as follows

1. ECM closes the EVAP purge valve and CVS valve which closes off the fuel vapor storage system. The vent pressure will increase due to the fuel vapor pressure in the fuel tank. If the fuel vapor pressure increase is more than the acceptable limit, the test will abort because a false leak test response will result.
2. Next, the purge valve is opened during engine idle allowing the fuel tank pressure to decrease due to purge operation.
3. ECM will perform the leak test measurement. The pressure recorded from the tests determines the extent of a possible leak. If leak test measurement is greater than a preset limit on two consecutive tests, the ECM will set the appropriate DTC and illuminate the MIL. The leak test measurement is only carried out during engine idle with the vehicle stationary. When leak test is complete, ECM opens the CVS valve, returning the system to normal purge operation.

ECM using an in-tank pressure sensor monitors pressure build-up to determine whether leaks are present. Possible reasons for a detected leak are

1. Fuel filler cap is not properly tightened or is missing.
2. There is an in-tank pressure sensor or actuator open circuit.
3. There is a short to battery voltage or ground.
4. Either purge or CVS valve is stuck open.
5. Either purge or CVS valve is stuck closed or there is a blocked line.
6. There is a loose, leaking, broken or disconnected EVAP system line.

If the EVAP system line is broken forward of the purge valve or is not connected, the engine may run rough and fueling adaptations will drift. The malfunction will not be detected by the ECM leak test, but by the ECM detection of a suspended fueling adaptation. The evaluation of EVAP system leakage is dependent on the differential pressure between fuel tank and ambient atmospheric pressure. The leak test is disabled at altitudes greater than 9500 feet.

If ECM detects a EVAP system leak, the following DTCs may be set

1. If DTC P0442 is set, a small leak has been detected within the EVAP system.
2. If DTC P0455 is set, a large leak has been detected within the EVAP system.

Check for poor connections, loose terminals, and open or shorted wires. Ensure EVAP canister purge valve or CVS valve is not sticky or blocked and that EVAP system lines are routed properly and not blocked or leaking. Ensure there are no EVAP system leaks. When DTC P0442 or P0455 repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "E" .

EVAP system includes a fuel tank pressure sensor and an EVAP Canister Vent Solenoid (CVS) valve, which is normally open. During EVAP system leak testing, ECM closes CVS valve and purge valve. ECM then monitors EVAP system pressure using fuel tank pressure sensor. If ECM detects a pressure decrease greater than a predetermined value, ECM will store a DTC. If EVAP CVS valve does not operate properly or a leak is detected, ECM will store a DTC.

CVS valve is mounted at the right side of the engine compartment. On Discovery Series II, battery voltage for CVS valve solenoid operation is supplied from Main relay and fuse No. 2 (15-amp) located in the engine compartment fuse/relay box. On Range Rover, battery voltage for CVS valve solenoid operation is supplied from Main relay and fuse No. 26 (20-amp) located in the engine compartment fuse/relay box. On all models, the ground connection is via the ECM which controls the CVS valve solenoid operation.

CVS valve is normally open, allowing any build up of pressure within EVAP system to escape, while keeping hydrocarbons in the EVAP canister. When the ECM is runs a fuel system test, the CVS valve is closed to seal the system. The ECM is then able to measure the pressure in the EVAP system using the fuel tank pressure sensor. ECM performs electrical integrity checks on the CVS valve to determine wiring or power supply malfunctions. The ECM can also detect a valve blockage if the signal from the fuel tank pressure sensor indicates a depressurizing fuel tank when the CVS valve should be open to the atmosphere.

The following failure modes are possible

1. Connector or harness wiring open or short circuit.
2. CVS valve stuck open or closed.
3. CVS valve blocked.

If ECM detects a CVS valve malfunction, the following DTCs may be set

1. If DTC P0446 is set, there is a blockage in the CVS valve, filter or line.
2. If DTC P0447 is set, there is a CVS valve open circuit.
3. If DTC P0448 is set, there is a CVS valve circuit shorted to ground.
4. If DTC P0449 is set, there is a CVS valve circuit shorted to battery voltage.

Check for poor connections, loose terminals, and open or shorted wires. Ensure CVS valve is not sticky or blocked and that EVAP system lines are routed properly and not blocked or leaking. When DTC P0446-P0449 repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "E" .

Fuel tank pressure sensor measures fuel tank pressure allowing ECM to systematically check EVAP system for leaks. Fuel tank pressure sensor is located on top of fuel tank with fuel pump and fuel gauge sending unit. Fuel tank pressure sensor is a non-serviceable item. If pressure sensor replacement is necessary, the complete fuel tank pump and sending unit must be replaced.

A fuel tank pressure sensor failure will not be noticed by the driver, but if ECM detects a malfunction, it will store a DTC in diagnostic memory and the MIL will be illuminated.

Possible failure symptoms of the fuel tank pressure sensor are as follows

1. Fuel tank pressure sensor poor performance.
2. Fuel tank pressure sensor low range malfunction.
3. Fuel tank pressure sensor high range malfunction.

Possible fuel tank pressure sensor failures are as follows

1. Damaged or blocked sensor.
2. Wiring harness or connector faulty.
3. Open circuit.
4. Short to battery voltage or ground.
5. ECM malfunction.

If fuel tank pressure sensor should malfunction, the following DTCs may be set

1. If DTC P0450 is set, a EVAP control system pressure sensor malfunction has been detected.
2. If DTC P0451 is set, poor fuel tank pressure sensor performance has been detected, indicated by sensor signal being stuck high within range.
3. If DTC P0452 is set, fuel tank pressure sensor signal is out of range (high) caused by a short to battery voltage.
4. If DTC P0453 is set, fuel tank pressure sensor signal is out of range (low) caused by a short to ground or an open circuit.

Note. Manufacturer does not recommend using any type of contact cleaner, preservative or sealant in an attempt to repair or correct poor electrical connections. Use of any of these materials will void manufacturer's warranty.

Check for poor connections, loose terminals, and open or shorted wires. See appropriate wiring diagram in WIRING DIAGRAMS article. (Scheme 7), (Scheme 8) and (Scheme 14). Perform repairs as necessary. When DTC P0450 repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "E". When DTC P0451-P0453 repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "A".

Relieve fuel pressure. See RELIEVING FUEL PRESSURE . Disconnect negative battery cable. Lower fuel tank to gain access to 3-pin connector on top of fuel tank. See FUEL PUMP in REMOVAL, OVERHAUL & INSTALLATION article. Check for poor connections, loose terminals, and open or shorted wires.

DTC P0460, P0461, P0462, P0463: FUEL LEVEL SENSOR MALFUNCTION

Note. If fuel gauge is not operating properly, fuel gauge must be repaired before proceeding with diagnostics and/or repairs.

Fuel level sensor is located in fuel tank next to fuel pump. On Defender and Discovery, fuel level sensor is activated when fuel pump relay is energized. On Range Rover, fuel level sensor is activated through Body Electric Control Module (BECM). On all models, fuel level sensor signal is used for fuel gauge display. On Discovery with Advanced EVAP system, fuel level sensor signal can be used to disable fuel system and HO2S diagnostics.

If fuel level sensor should malfunction, the following DTCs may be set

1. If DTC P0460 is set, a fuel level sensor circuit malfunction has been detected.
2. If DTC P0461 is set, the poor fuel level sensor performance or signal out of expected range has been detected.
3. If DTC P0462 is set, the fuel level sensor has a low input signal caused by an open circuit.
4. If DTC P0463 is set, the fuel level sensor has a high input signal caused by a short to battery voltage or to ground.

Note. Fuel level sender signal input is required by ECM as part of the misfire detection strategy if a low fuel situation was present when misfire was detected and logged as a fault. The signal is received as an analogue signal from the fuel tank sender unit.

Check for poor connections, loose terminals, and open or shorted wires. See appropriate wiring diagram in WIRING DIAGRAMS article. Perform repairs as necessary. Check sensor resistance and sensor signal voltage. See FUEL LEVEL SENDER RESISTANCE & SIGNAL VOLTAGE table. When DTC P0460-P0461 repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "C" . When DTC P0462-P0463 repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "A" .

FUEL LEVEL SENDER RESISTANCE & SIGNAL VOLTAGE

The VSS is used, by the ECM, to control idle speed and over-run cut off. The ECM receives the signal through a hard wired connection direct from the Self Leveling and Anti-Lock Brake System (SLABS) ECU. On vehicles equipped with A/T, there are 2 vehicle speed signals received by the ECM. The second signal originates at the transmission output shaft speed sensor. It is sent to the ECM from the Electronic Automatic Transmission (EAT) ECU though the Controller Area Network (CAN). The ECM compares the vehicle speed signal generated by the SLABS ECU with that from the EAT ECU and information from the transfer case. This allows the ECM to consider vehicle speeds during low range gearing and compensate as necessary.

Vehicle speed signal generated by the SLABS ECU is a zero to battery voltage Pulse Width Modulated (PWM) signal. Signal pulses are generated 8000 times per mile, with a signal frequency that changes with road speed. At zero MPH the ECU outputs a 2 Hz reference signal for diagnostic purposes.

The VSS can fail in the following ways

1. An open circuit.
2. Short to battery voltage or ground.

In the event of a VSS failure, any of the following symptoms may be observed

1. MIL illuminated after 2 driving cycles.
2. SLABS/HDC warning lamp illuminated and audible warning.

If vehicle speed sensor should malfunction, the following DTCs may be set

1. If DTC P0500 is set, there is a vehicle speed sensor malfunction caused by VSS short or open circuit.
2. If DTC P0501 is set, there is a vehicle speed sensor range or performance malfunction indicated by VSS signal that is not within expected range.
3. If DTC P0502 is set, there is a vehicle speed sensor low input signal caused by an open circuit.

On Discovery Series II, VSS input signal from the SLABS ECU is measured at ECM 40-pin connector C0637 terminal No. 22 (Pink/Green wire). VSS input signal is a PWM zero to battery voltage signal. There is a high-line and a low-line bi-directional VSS input signal from the EAT ECU sent using the CAN data bus. The high-line signal from EAT ECU connector terminal No. 16 (White wire) is 2.5-5.0 volts and is measured at ECM 40-pin connector C0637 terminal No. 36 (White wire). The low-line signal from EAT ECU connector terminal No. 44 (Yellow wire) is 0.0-2.5 volts and is measured at ECM 40-pin connector C0637 terminal No. 37 (Yellow wire).

On Range Rover, VSS input signal from the BECM is measured at ECM 40-pin connector C0637 terminal No. 22 (Yellow wire). VSS input signal is a PWM zero to battery voltage signal. There is a high-line and a low-line bi-directional VSS input signal from the EAT ECU sent using the CAN data bus. The high-line signal from EAT ECU connector terminal No. 16 (Yellow/Black wire) is 2.5-5.0 volts and is measured at ECM 40-pin connector C0637 terminal No. 36 (Yellow/Black wire). The low-line signal from EAT ECU connector terminal No. 44 (Yellow/Brown wire) is 0.0-2.5 volts and is measured at ECM 40-pin connector C0637 terminal No. 37 (Yellow/Brown wire).

On all models, if there is a VSS malfunction, ECM applies default values derived from the EAT ECU. Check VSS circuits for opens or shorts and repair as necessary. See appropriate wiring diagram in WIRING DIAGRAMS article. If circuits are okay, replace VSS and recheck. When DTC P0500-P0502 repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "B" .

Note. The IAC rotary valve must not be forced to move by mechanical means. The actuator can not be serviced; if defective, the entire IAC valve must be replaced as a unit.

IAC valve is used to maintain idle speed under all operating conditions. IAC valve uses 2 coils that use opposing PWM signals to control the opening and closing position of a rotary valve. If one of the PWM signal circuits fails, ECM closes down the remaining signal preventing the IAC valve from working at its maximum or minimum setting. If this should occur, the IAC valve automatically resumes a default idle position. In this condition, the engine idle speed is increased and maintained at 1200 RPM with no engine load. The cold start idle speed is held at 1200 RPM in neutral for approximately 20 seconds and ignition timing is retarded as a catalyst heating strategy. The cold start idle speed and the default idle speed position give the same engine speed. Although the idle speed is the same they must not be confused with each other as they are set separately by the ECM.

IAC valve diagnostic checks performed by the ECM are as follows

1. Opening coil output short circuit to ground.
2. Opening coil output short circuit to battery supply.
3. Opening coil output open circuit.
4. Closing coil output short circuit to ground.
5. Closing coil output short circuit to battery voltage.
6. Closing coil output open circuit.
7. If engine speed is 100 RPM less than the target speed, engine load is less than 2.5 and the measured air flow is more than 2.8 kg/s less than the expected air flow a DTC will be set as a blocked IAC valve with a low RPM error.
8. If engine speed is more than 180 RPM greater than the target speed and the measured air flow is more than 2.8 kg/s greater than the expected air flow for a DTC will be set as a blocked IAC valve with a high RPM error.

IAC valve can fail or supply an incorrect signal in the following ways

1. Actuator malfunction.
2. Rotary valve seized.
3. Wiring harness or connector fault.
4. Intake air system air leak.
5. Blocked, restricted or crimped actuator port or hoses.

In the event of an IAC valve signal failure any of the following symptoms may be observed

1. Either low or high idle speed.
2. Engine stalls or difficult starting.
3. Idle speed in default condition.

If there is an idle control system should malfunction, the following DTCs may be set

1. If DTC P0505 is set, there is an idle control system malfunction there is a blocked IAC valve indicated by a high or low RPM error.
2. If DTC P1509 or DTC P1510 are set, there is an IAC valve opening coil malfunction caused by an opening winding malfunction.
3. If DTC P1513 or DTC P1514 are set, there is an IAC valve opening coil malfunction caused by an opening winding short to ground.
4. If DTC P1550 or DTC P1551 are set, there is an IAC valve closing coil malfunction caused by a closing winding malfunction.
5. If DTC P1552 or DTC P1553 are set, there is an IAC valve closing coil malfunction caused by a closing winding short to ground.

IAC valve is located on the side of the air inlet pipe on top of the engine. On Discovery Series II, battery voltage for IAC valve solenoid operation is supplied from Main relay and fuse No. 1 (30-amp) located in the engine compartment fuse/relay box to IAC valve 3-pin connector terminal No. 2 (Brown/Orange wire). On Range Rover, battery voltage for IAC valve solenoid operation is supplied from Main relay and fuse No. 37 (30-amp) located in the engine compartment fuse/relay box to IAC valve 3-pin connector terminal No. 2 (Brown/Orange wire). On all models, the ground connections are via the ECM which controls the IAC valve solenoid operation. IAC valve open signal is controlled at ECM 52-pin connector C0636 terminal No. 42 (Blue/Gray wire). IAC valve closed signal is controlled at ECM 52-pin connector C0636 terminal No. 43 (Red/Green wire).

Check for poor connections, loose terminals, and open or shorted wires. See appropriate wiring diagram in WIRING DIAGRAMS article. (Scheme 7), (Scheme 8) and (Scheme 11). Perform repairs as necessary. Check IAC valve control voltage. See appropriate wiring diagram in WIRING DIAGRAMS article. When DTC P0505 repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "C". When DTC P1509, P1510, P1513, P1514 & P1550-P1553 repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "A".

When ignition is turned to ON position battery voltage is applied to charging system fault indicator. Indicator will go out when generator begins to operate.

If there is a system voltage malfunction, the following DTCs may be set

1. If DTC P0560 is set, there is a system voltage malfunction.
2. If DTC P0561 is set, system voltage unstable.
3. If DTC P0562 is set, system voltage low.
4. If DTC P0563 is set, the system voltage high.

Check condition of battery, charging system, and fuses. When DTC P0560-P0563 repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "A" .

Controller Area Network (CAN) system is a high speed serial interface between the ECM and the Electronic Automatic Transmission (EAT) ECU. The CAN system uses a data bus to transmit information messages between ECM and EAT ECU. Because there are only two components in this CAN system, one will transmit information messages and the other will receive information messages, and vice-versa.

The CAN system uses a twisted pair of wires to form the data bus to reduce electrical interference. The information messages are structured so that each of the receivers (ECM or EAT ECU) is able to interpret and react to the messages sent.

CAN system is used by the EAT ECU and ECM for transmission of the following information

1. Gearshift torque control information.
2. Gear selected and gear change information.
3. EAT OBD information and MIL illumination request.
4. Vehicle speed signal.
5. Engine torque and speed.
6. Engine coolant temperature.
7. Intake air temperature.
8. Altitude adaptation factor.
9. Throttle angle and/or pedal position.

CAN data bus high-line signal is connected between ECM 40-pin connector C0637 terminal No. 36 (Yellow/Black wire) and EAT ECU 88-pin connector terminal No. 16 (Yellow/Black wire). CAN data bus low-line signal is connected between ECM 40-pin connector C0637 terminal No. 37 (Yellow/Brown wire) and EAT ECU 88-pin connector terminal No. 44 (Yellow/Brown wire). CAN system can fail as a result of an open or short circuit in the CAN data bus wiring.

In the event of a CAN data bus failure any of the following symptoms may be observed

1. MIL will be illuminated after 2 drive cycles.
2. EAT ECU defaults to 3rd gear only.
3. Harsh gearshifts.
4. SPORT and MANUAL indicator lights flash alternately.

If there is a Controller Area Network (CAN) malfunction the following DTCs may be set

1. If DTC P0600 is set, there is a serial communication link malfunction, indicated by CAN time out.
2. If DTC P1776 is set, there is a transmission control system torque interface malfunction EAT torque interface error.

Check for poor connections, loose terminals, and open or shorted wires. See appropriate wiring diagram in WIRING DIAGRAMS article. (Scheme 7), (Scheme 8) and (Scheme 18). Perform repairs as necessary. When DTC P0600 and P1776 repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "A".

Scheme 18

If there is a Controller Area Network (CAN) malfunction the following DTCs may be set

1. If DTC P0601 is set, there is an internal ECM memory check sum error.
2. If DTC P0603 is set, there is an internal ECM keep alive memory Random Access Memory (RAM) error.
3. If DTC P0604 is set, there is an internal ECM RAM error.
4. If DTC P0606 is set, there is a ECM processor malfunction.

Manufacture does not provide specific repair information. Check for poor power and ground connections and/or loose wires at ECM connectors. See appropriate wiring diagram in WIRING DIAGRAMS article. (Scheme 7)and (Scheme 8). Perform repairs as necessary. When DTC P0601, P0603 or P0604 repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "A". When DTC P0606 repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "B".

When ignition is turned to ON position, ECM carries out a Amber SERVICE ENGINE SOON/MIL self-test. As a bulb check, MIL will illuminate for 3 seconds when ignition switch is turned to ON position and should go out if no DTCs are detected. If a DTC is detected the MIL will be will go out for one second before illuminating again to indicate a DTC exists.

On Discovery Series II, battery voltage is supplied to instrument cluster and MIL from fuse No. 27 (10-amp), located in passenger compartment fuse/relay box. ECM controls MIL operation by providing a MIL ground path at ECM 40-pin connector C0637 terminal No. 20 (Red/Gray wire). Voltage at instrument cluster when MIL is illuminated should be less than 1.8 volts and more than 7.7 volts when MIL is off. Battery voltage is supplied to fuse No. 27 from fusible link No. 8 (50-amp) when ignition switch is in ON position.

On Range Rover, battery voltage is supplied to instrument cluster and MIL from fuse No. 1 (10-amp), located in Body Electrical Control Module (BECM). ECM controls MIL operation by providing a MIL ground path at ECM 40-pin connector C0637 terminal No. 20 (White/Blue wire).

If MIL does not illuminate during bulb check or engine does not start, anti-theft immobilizer system (if equipped) may be activated. If MIL does not illuminate during bulb check and/or DTC P0650 is set, ensure bulb is okay. If bulb is okay check for an open or short in power circuit between fuse and MIL. If power circuit is okay, check for an open or short in control circuit between MIL and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. When DTC repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "A" .

ECM uses CKP sensor signal to determine engine speed. ECM shares the engine speed information with the Electronic Automatic Transmission (EAT) ECU, tachometer located in instrument cluster, Body Electrical Control Module (BECM) by transmitting the data via the CAN link. On Discovery Series II, engine speed output signal is scaled down to 2 pulses per crankshaft revolution and sent to the tachometer. On Range Rover, engine speed output signal is scaled down to 4 pulses per crankshaft revolution and sent to the tachometer.

Engine speed signal output signal is a 0.0-5.0 volt PWM sent from ECM 40-pin connector C0637 terminal No. 17 (White/Gray wire on Discovery; Gray wire on Range Rover) to BECM.

Manufacture does not provide specific repair information. Check for poor power and ground connections and/or loose wires at ECM connectors. Perform repairs as necessary. When DTC P0601, P0603 or P0604 repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "A" .

DTC P1129: PRIMARY HO2S CIRCUIT MALFUNCTION

See DTC P0130-P0138, PO140-P0141, P0150-P0158, P0160-P161, P1129, P1170 & P1173: HO2S CIRCUIT MALFUNCTION .

DTC P1170, P1173: DOWNSTREAM FUEL TRIM MALFUNCTION

See DTC P0130-P0138, PO140-P0141, P0150-P0158, P0160-P161, P1129, P1170 & P1173: HO2S CIRCUIT MALFUNCTION .

DTC P1171, P1172: SYSTEM TOO LEAN OR RICH (BANK 1)

See DTC P0170-P0175, P1171-P1172 & P1174-P1175: FUEL TRIM MALFUNCTION, SYSTEM TOO LEAN OR RICH .

DTC P1174, P1175: SYSTEM TOO LEAN OR RICH (BANK 2)

See DTC P0170-P0175, P1171-P1172 & P1174-P1175: FUEL TRIM MALFUNCTION, SYSTEM TOO LEAN OR RICH .

DTC P1230, P1231, P1232: FUEL PUMP RELAY MALFUNCTION

Refer to TestBook for specific repair information. When DTC P1230-P1232 repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "A" .

The fuel pump relay is a 4-pin normally open relay located in the engine compartment fuse/relay box. Fuel pump relay controls the fuel pump operation, regulating fuel supply to fuel injectors. When ignition switch is turned on and the engine is cranked, the ECM activates the fuel pump relay, allowing fuel system to be pressurized to 52 psi (3.6 kPa). The ECM then deactivates the relay until the engine has started and fuel pressure decreases. If the fuel pump operates, but the fuel pressure is out of limits, adaptive fuel faults will be stored.

If there is a fuel pump relay failure any of the following symptoms may be observed

1. The engine stalls or will not start.
2. There is no fuel pressure at the fuel injectors.

On Discovery Series II, battery voltage is supplied to fuel pump relay drive circuit when main relay is energized through engine compartment fuse/relay box internal circuits. When fuel pump relay is energized, battery voltage from fuse No. 10 (30-amp) is supplied to fuel pump. Fuel pump relay is energized when ECM provides a ground at ECM 24-pin connector C0635 terminal No. 18 (Blue/Purple wire).

On Range Rover, battery voltage is supplied to fuel pump drive circuit through fuse No. 39 (20-amp) to fuel pump relay and inertia fuel cut-off switch when main relay is energized. Fuel pump relay is energized when ECM provides a ground at ECM 24-pin connector C0635 terminal No. 18 (Blue/Purple wire).

Fuel pump relay can fail the following ways or supply incorrect signal

1. Fuel pump relay drive open circuit.
2. Short circuit to ground.
3. Short circuit to battery voltage.

If there is a fuel pump relay malfunction the following DTCs may be set

1. If DTC P1230 is set, there is a fuel pump relay malfunction caused by a fuel pump relay open circuit and not the fuel pump.
2. If DTC P1231 is set, the fuel pump relay circuit is low caused by a fuel pump relay short to battery voltage and not the fuel pump.
3. If DTC P1232 is set, the fuel pump relay circuit is high caused by a fuel pump relay short to ground and not the fuel pump.

Note. If inertia fuel cut-off switch is tripped, fuel pump will not be energized. On Discovery Series II, inertia switch is located in the engine compartment. On Range Rover, inertia switch is located behind passenger side kick panel. On all models, to reset inertia switch, press down on the rubber top.

Check for poor power and ground connections and/or loose wires at ECM and engine compartment fuse/relay box connectors. See appropriate wiring diagram in WIRING DIAGRAMS article. (Scheme 7)and (Scheme 8). When DTC P1230-P1232 repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "A".

DTC P1300, P1301, P1302, P1303, P1304, P1305, P1306, P1307, P1308 & P1319: MISFIRE DETECTED

See DTC P0300-P0308, P1300-P1308 & P1319: MISFIRE DETECTED IN ONE OR MORE CYLINDERS .

SAI control valves are located on brackets at each side of the engine. SAI air injection supply pipes connect to a large port on the side of each SAI control valve via a short rubber connection hose. A small vacuum port is located on each SAI control valve opposite the air injection supply port. Vacuum supply to each vacuum operated SAI control valve is through small nylon hoses from the SAI vacuum solenoid valve. An intermediate connector is included in the vacuum hose to split the vacuum applied to each vacuum operated valve, so that both valves open and close simultaneously.

When vacuum is applied to SAI control valves, the valve opens to allow the pressurized air from the SAI pump through to the exhaust manifolds. The injection air is output from each SAI control valve through a port in the bottom of each unit. A metal pipe connects the output port of each SAI control valve and each exhaust manifold via an intermediate "T" fitting. The "T" fitting splits the pressurized air delivered to the two center exhaust ports on each cylinder head. The pipes between the "T" fitting and the exhaust manifold are enclosed in thermal sleeving to protect the surrounding components from the heat of the exhaust gases. When the SAI vacuum solenoid valve is de-energized, the vacuum supply line opens to atmosphere, causing the vacuum operated valves to close automatically.

If the vacuum operated SAI control valves malfunction (i.e.: from a disconnected or blocked SAI delivery pipe or vacuum hose, etc.) which prevents air delivery to exhaust manifolds, the following DTCs may be set

1. If DTC P1412 is set, there is a SAI system fault on the left side indicated by no air delivery to catalysts.
2. If DTC P1413 is set, there is a SAI system fault on the left side indicated by no air delivery to catalysts.
3. If DTC P1414 is set, there is a SAI system fault on the left side indicated by no air delivery to catalysts.
4. If DTC P1415 is set, there is a SAI system fault on the right side indicated by no air delivery to catalysts.
5. If DTC P1416 is set, there is a SAI system fault on the right side indicated by no air delivery to catalysts.
6. If DTC P1417 is set, there is a SAI system fault on the right side indicated by no air delivery to catalysts.

Check air delivery pipe and vacuum hose connections for leaks or breaks. Ensure air delivery pipes and vacuum hoses are not bent, crushed or blocked. Perform repairs as necessary. When DTC P1412-P1417 repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "A" .

DTC P1509, P1510, P1513, P1514: IDLE AIR CONTROL (IAC) VALVE OPENING STEPPER MOTOR MALFUNCTION

See DTC P0505, P1509, P1510, & P1550-P1553: IDLE CONTROL SYSTEM MALFUNCTION .

Request for A/C operation is signaled to Heating and Ventilation Air Conditioning (HVAC) control unit and ECM when A/C control panel switch is pressed, completing a ground path. Battery voltage to A/C control panel switch is supplied via ECM 40-pin connector C0637 terminal No. 38 (Purple/White wire on Discovery Series II; Yellow/Black wire on Range Rover). When A/C operation request is received, A/C compressor clutch will be engaged based on other operating requirements. If there is an A/C request failure, the A/C system will not work even if all other requirements are met.

The A/C compressor clutch relay is a 4-pin normally open relay located in the engine compartment fuse box. When the ECM grounds A/C clutch relay coil the switching contacts close o allow the relay contacts to close and the A/C clutch to receive battery voltage. When the ECM opens the ground path, the clutch relay will be de-energized and shut down A/C compressor clutch. Battery voltage to A/C clutch relay is supplied via fuse No. 6 (10-amp) located in the engine compartment fuse/relay box. Battery voltage to A/C clutch relay coil is supplied from the main relay, also located in the engine compartment fuse/relay box. A/C clutch relay coil ground is supplied via ECM 40-pin connector terminal No. 29 (Black/Gray wire on Discovery Series II; Black/Green wire on Range Rover). When the relay is energized the output from the switching contacts goes directly to the A/C compressor clutch. If there is an A/C clutch relay failure, the A/C system will not work even if all other requirements are met.

The A/C request can fail because of the following

1. An open circuit.
2. A short circuit to battery voltage.
3. A short circuit to ground.
4. A wiring harness problem.

The A/C clutch relay can fail because of the following

1. There is an A/C clutch relay open circuit.
2. There is a short circuit to battery voltage.
3. There is a short circuit to ground.
4. There is a broken A/C clutch relay return spring.

If there is an A/C request failure, the following DTC may be set

1. If DTC P1535 is set, there is an A/C compressor request malfunction when A/C operation is first requested when A/C is not in standby mode.

If there is an A/C compressor clutch relay operation malfunction, the following DTCs may be set

1. If DTC P1536 is set, there is an A/C compressor operation request signal range or performance problem caused by a clutch relay open circuit.
2. If DTC P1537 is set, there is an A/C compressor operation request input signal that is too low caused by a short to ground.
3. If DTC P1538 is set, there is an A/C compressor operation request input signal that is too high caused by a short to battery voltage.

Check for poor power and ground connections and/or loose wires at ECM and engine compartment fuse/relay box connectors. See appropriate wiring diagram in WIRING DIAGRAMS article. (Scheme 7)and (Scheme 8). When DTC P1535-P1538 repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "A".

DTC P1550, P1551, P1552, P1553: IDLE AIR CONTROL (IAC) VALVE CLOSING STEPPER MOTOR MALFUNCTION

See DTC P0505, P1509, P1510, & P1550-P1553: IDLE CONTROL SYSTEM MALFUNCTION .

When the vehicle travels across rough terrain, or on rough roads the ECM could falsely interpret suspension vibrations as a misfire and invoke engine misfire protocols and/or set a false DTC. The Self-Leveling and Anti-Lock Brake System (SLABS) ECU sends a rough road PWM signal to the ECM. Based on this rough road PWM signal, the ECM can suspend misfire detection for as long as the vehicle is travelling on a rough road.

Rough road signal input is measured at ECM 40-pin connector C0637 terminal No. 34 (Red/Green wire on Discovery Series II; Yellow/Pink wire on Range Rover). The SLABS ECU rough road PWM signal varies in accordance with changing road conditions. The rough road PWM signal operates at a frequency of 2.10-2.56 Hz. ECM rough road control is based on specific changes to the PWM signal. If there is a rough road PWM signal failure the Hill Descent Control/Anti-Lock Braking System (HDC/ABS) warning light may be illuminated.

The rough road PWM signal can fail in the following ways

1. Harness or connector damage.
2. SLABS wheel speed sensor failure.

If there is a rough road signal malfunction, the following DTCs may be set

1. If DTC P1590 is set, there is an ABS rough road signal circuit malfunction. Hardware is okay, but the SLABS ECU is sending an error signal.
2. If DTC P1591 is set, there is a low ABS rough road signal circuit. Signal from SLABS ECU is shorted to ground.
3. If DTC P1592 is set, there is a high ABS rough road signal circuit. Signal from SLABS ECU shorted circuit to battery voltage.

When ignition is turned on and during vehicle operation ECM checks rough road signal circuits. If expected signal is not seen, ECM will store a DTC. Using an oscilloscope or Snap-On PAC ensure SLABS ECU PWM signal indications are consistent with road conditions. See ROUGH ROAD PWM SIGNAL INDICATIONS table. If PWM signal is not as specified, check circuits for opens or shorts. Check for poor power and ground connections and/or loose wires at ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Ensure ABS wheel speed sensors are operating properly. Repair as necessary. When DTC P1590-P1592 repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "A" .

ROUGH ROAD PWM SIGNAL INDICATIONS

The ECM transmits throttle angle, engine torque, engine identification, and transmission type data to the SLABS ECU to support the Hill Descent Control (HDC) system. The data is transmitted via a 0-12 volt PWM signal at a frequency of 179.27 Hz.

HDC signal output is from ECM 52-pin connector C0636 terminal No. 29 (Gray/Purple wire). The ECM generates a PWM signal that varies in pulse width in accordance with changing throttle angle or engine torque. The throttle angle data is transmitted on pulses 1, 3, 5 and 37. The engine torque data is transmitted on pulses 2, 4, 6 and 38. The type of engine and transmission information is transmitted on pulse 39. A synchronizing pulse is transmitted after every 39th pulse.

The HDC signal can fail because of the following

1. Wiring harness or connector damage.

A HDC signal failure may be indicated by the following

1. HDC/ABS warning light illuminated.
2. HDC inoperative and an audible warning.

If there is a HDC signal malfunction the following DTCs may be set

1. If DTC P1663 is set, there is a throttle angle/engine torque signal circuit malfunction caused by an open circuit in the SLABS HDC link.
2. If DTC P1664 is set, there is a throttle angle/engine torque signal circuit low voltage caused by a short circuit to ground in the SLABS HDC link.
3. If DTC P1665 is set, there is a throttle angle/engine torque signal circuit high voltage caused by a short circuit to battery voltage in the SLABS HDC link.

Check for opens or shorts. Check for poor connections and/or loose wires at ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. When DTC P1663-P1665 repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "A" .

ECM and Body Control Unit (BCU) security system comprise the immobilization system. The ECM and BCU combine to prevent the engine from operating unless the appropriate security criteria are met. The ECM and BCU are a matched pair, if either one is replaced for any reason, the system will not operate unless the replaced unit is correctly synchronized to its original specification. A Land Rover TestBook must be used to reconfigure and synchronize the immobilization system. The ECM operates the vehicle immobilization system in a NEW, SECURE or NO CODE state.

When the ECM operating in the NEW state, a Land Rover TestBook is required to instruct the ECM to learn a new BCU code. If the ECM is a NEW replacement direct from the supplier, it will not operate the vehicle and will store a new ECM DTC when it is installed. This DTC must be cleared after instructing the ECM to learn the BCU code using TestBook.

When the ECM is operating in the SECURE state, no further action is required as the ECM has successfully learned the BCU code. A SECURE ECM can not be configured to a NO CODE state. If the vehicle has an ECM with a valid code, the engine will start and the MIL will go out. If the ECM has an invalid BCU security code the engine will crank, start, and then immediately stall. The status of the security system can only be determined using Land Rover TestBook. The immobilization serial "W" link signal input is at ECM 40-pin connector C0637 terminal No. 33 (Light Green/Gray wire).

If there is an anti-theft signal circuit malfunction the following DTCs may be set

1. If DTC P1666 is set, there is an engine anti-theft signal circuit malfunction caused by a BCU serial link frame or bit timing error.
2. If DTC P1667 is set, there is an engine anti-theft signal circuit low voltage caused by a serial link short circuit to ground.
3. If DTC P1668 is set, there is an engine anti-theft signal circuit high voltage caused by a serial link open circuit.
4. If DTC P1672 is set, there is an engine anti-theft signal circuit wrong code received with ECM is SECURE state.
5. If DTC P1673 is set, there is an engine anti-theft signal NEW ECM not configured after a NEW ECM has been installed.
6. If DTC P1674 is set, there is an engine anti-theft signal NO CODE ECM, after a valid code has been received from BCU.

A Land Rover TestBook must be used to reconfigure and synchronize the immobilization system. Check circuits for opens or shorts. Check for poor connections and/or loose wires at ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. When DTCs P1666-P1668 and/or DTCs P1672-P1674 repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "A" .

On Range Rover, the ECM is located at the left corner of the engine compartment inside an "E" box. The ECM "E" box is equipped with a cooling fan that provides cooler cabin air into the "E" box to provide a cooler environment for the Bosch Motronic 5.2.1 ECM. "E" box cooling fan operation is controlled by the ECM. The operating temperature of the ECM is monitored by an internal temperature sensor which it uses to determine when "E" box cooling fan operation is necessary.

When cooling fan operation is needed the fan is grounded through ECM 40-pin connector C0637 terminal No. 10 (Black/Pink wire). Battery voltage for cooling fan is provided from fuse No. 26 (20-amp) located in engine compartment fuse/relay box via Brown/Pink wire.

If there is an "E" box cooling fan malfunction the MIL will illuminate and the following DTCs may be set

1. If DTC P1669 is set, the ECM cooling fan circuit malfunction.
2. If DTC P1670 is set, the ECM cooling fan circuit low.
3. If DTC P1671 is set, the ECM cooling fan circuit high.

Ensure "E" box cooling fan is operating properly. Check for opens or shorts. Check for poor connections and/or loose wires at ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. When DTCs P1669-P1671 repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "A" .

When an OBD relevant error is detected within the transfer case Electronic Control Unit (ECU), a MIL illumination request is sent to ECM. If transfer case cannot move into high range, an incorrect transfer motor position is detected or a vehicle speed sensor malfunction is detected and the ECM will store a DTC. MIL will illuminate if malfunctions are detected during 2 drive cycles. Each time the ignition is turned on (power-up) the ECM checks the signal line. The transfer case ECU is located under the left front seat and has one 36-pin harness connector.

Manufacturer does not provide specific diagnosis and repair information. When DTC P1700 repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "B" . When DTC P1701-P1703 and/or P1708 repairs are completed, perform REPAIR CONFIRMATION DRIVE CYCLE "A" .

See also:
• ECM CONNECTOR IDENTIFICATION
• REPAIR CONFIRMATION DRIVE CYCLE
• DTC P0111, P0112, P0113
• DTC P0120, P0122, P0123
• DTC P0340
• DTC P0460, P0461, P0462, P0463
• DTC P1129
• DTC P1170, P1173
• DTC P1171, P1172
• DTC P1174, P1175
• DTC P1230, P1231, P1232
• DTC P1300, P1301, P1302, P1303, P1304, P1305, P1306, P1307, P1308 & P1319
• DTC P1509, P1510, P1513, P1514
• DTC P1550, P1551, P1552, P1553
• REPAIR CONFIRMATION DRIVE CYCLE "A"
• REPAIR CONFIRMATION DRIVE CYCLE "B"
• REPAIR CONFIRMATION DRIVE CYCLE "C"
• REPAIR CONFIRMATION DRIVE CYCLE "E"
• RELIEVING FUEL PRESSURE