Discovery 2. Manual — part 75

ENGINE MANAGEMENT SYSTEM - V8

DESCRIPTION AND OPERATION 18-2-29

In the event of a TP sensor signal failure any of the following symptoms may be observed:

l

Engine performance concern.

l

Delayed throttle response.

l

Failure of emission control.

l

Closed loop idle speed control inoperative.

l

Automatic gearbox kickdown inoperative.

l

Incorrect altitude adaptation.

l

MIL illuminated (NAS only).

There are three throttle position sensor diagnostic checks:

l

TP sensor signal is greater than the maximum threshold value – the engine speed must be greater than 400 rev/
min for longer than 2 seconds and the signal must be greater than 96% for longer than 50 ms.

l

TP sensor signal is less than the minimum threshold – the engine speed must be greater than 400 rev/min for
longer than 2 seconds and the signal must be less than 4% for longer than 50 ms.

l

Ratio of throttle position to mass of air flow – the calculated throttle angle must be outside limits when the engine
speed is between 800 rev/min and 4000 rev/min, the engine load is between 2 and 6.5 and the coolant
temperature is above -10

°

C (14

°

F).

Should a malfunction of the TP sensor occur the following fault codes may be evident and can be retrieved by
TestBook.

P code

J2012 description

Land Rover description

P0101

Mass or volume air flow circuit range/
performance problem

Load monitoring, the ratio of throttle position to air flow

P0122

TPS a circuit low input

Signal < minimum threshold

P0123

TPS a circuit high input

Signal > maximum threshold

ENGINE MANAGEMENT SYSTEM - V8

18-2-30 DESCRIPTION AND OPERATION

Heated Oxygen Sensors (HO

2

S) (C0642)

The market requirement dictates how many HO

2

S are fitted to the vehicle.

l

4 sensors are fitted to all NAS and EU-3 vehicles.

l

2 sensors fitted to all UK, European, Australia and Japanese pre EU-3 specification vehicles.

l

No sensors fitted to ROW vehicles.

The HO

2

S monitor the oxygen content of the exhaust gases. By positioning the sensors one for each bank upstream

of the catalytic converter in the exhaust pipe, the ECM can control fuelling on each bank independently of the other.
This allows greater control of the air:fuel ratio and maintains optimum catalyst efficiency. On NAS vehicles the ECM
also uses two HO

2

S positioned downstream of the catalytic converters in the exhaust pipe to monitor catalytic

converter efficiency. The ECM is able to achieve this by comparing the values of the upstream HO

2

S and the down

stream sensor for the same bank. These comparative values form part of the ECM OBD strategy.

The HO

2

S uses zirconium contained in a galvanic cell surrounded by a gas permeable ceramic, this produces an

output voltage proportional to the ratio difference between the oxygen in the exhaust gases and to the ambient
oxygen.

The HO

2

S operates at approximately 350

°

C (662

°

F). To achieve this temperature the HO

2

S incorporate a heating

element which is controlled by a PWM signal from the ECM. The elements are activated immediately after engine
starts and also under low engine load conditions when the exhaust gas temperature is insufficient to maintain the
required HO

2

S temperature. If the heater fails, the ECM will not allow closed loop fuelling to be implemented until the

sensor has achieved the required temperature.

This value equates to an HO

2

S output of 450 to 500 mV. A richer mixture can be shown as

λ

= 0.97, this pushes the

HO

2

S output voltage towards 1000 mV. A leaner mixture can be shown as

λ

= 1.10, this pushes the HO

2

S output

voltage towards 100 mV.

From cold start, the ECM runs an open loop fuelling strategy. The ECM keeps this strategy in place until the HO

2

S is

at a working temperature of 350

°

C (662

°

F). At this point the ECM starts to receive HO

2

S information and it can then

switch into closed loop fuelling as part of its adaptive strategy. The maximum working temperature of the tip of the
HO

2

S is 930

°

C (1706

°

F), temperatures above this will damage the sensor.

HO

2

S age with use, this increases their response time to switch from rich to lean and from lean to rich. This can lead

to increased exhaust emissions over a period of time. The switching time of the upstream sensors are monitored by
the ECM. If a pre-determined threshold is exceeded, a failure is detected and the MIL illuminated.

+

EMISSION CONTROL - V8, DESCRIPTION AND OPERATION, Exhaust Emission Control System.

Input/Output
The upstream and downstream HO

2

S are colour coded to prevent incorrect fitting. The tips of the upstream sensors

are physically different to the tips of the downstream sensors.

The HO

2

S are colour coded as follows:

l

Upstream sensors (both banks) - orange.

l

Downstream sensors (both banks) - grey.

The four HO

2

S have a direct battery supply to the heater via fuse 2 located in the engine compartment fuse box.

ENGINE MANAGEMENT SYSTEM - V8

DESCRIPTION AND OPERATION 18-2-31

The heater is driven by the ECM providing an earth path for the circuit as follows:

l

Upstream LH bank via pin 19 of connector C0635 of the ECM.

l

Upstream RH bank via pin 13 of connector C0635 of the ECM.

l

Downstream LH bank via pin 7 of connector C0635 of the ECM.

l

Downstream RH bank via pin 1 of connector C0635 of the ECM.

The HO

2

S output signal is measured by the ECM as follows:

l

Upstream LH bank via pin 15 of connector C0635 of the ECM.

l

Upstream RH bank via pin 16 of connector C0635 of the ECM.

l

Downstream LH bank via pin 17 of connector C0635 of the ECM.

l

Downstream RH bank via pin 14 of connector C0635 of the ECM.

The HO

2

S earth path for the signal is supplied by the ECM as follows:

l

Upstream LH bank via pin 9 of connector C0635 of the ECM.

l

Upstream RH bank via pin 10 of connector C0635 of the ECM.

l

Downstream LH bank via pin 11 of connector C0635 of the ECM.

l

Downstream RH bank via pin 8 of connector C0635 of the ECM.

The HO

2

S voltage is difficult to measure using a multimeter, the output can be monitored using TestBook. A rich

mixture would read 500 to 1000 mV, a weak mixture would read 100 mV to 500 mV, the reading should switch from
rich to weak. The open loop default voltage is 450 mV, this is used by the ECM to set the air/ fuel ratio until the tip of
the HO

2

S reaches operating temperature.

The HO

2

S can fail the following ways or supply incorrect signal:

l

Sensor open circuit.

l

Short circuit to vehicle supply.

l

Short circuit to vehicle earth.

l

Sensor disconnected.

l

Stoichiometric ratio outside the correct operating band.

l

Contamination from leaded fuel.

l

Air leak into the exhaust system.

l

Wiring loom damage.

l

Sensors fitted incorrectly or cross wired.

In the event of a HO

2

S signal failure any of the following symptoms may be observed:

l

Default to open loop fuelling on defective bank.

l

If the sensors are crossed over (LH bank to RH bank), the engine will run normally after initial start up, but
performance will become progressively worse as the sensors go towards maximum rich for one bank of cylinders
and maximum lean for the other. The ECM will eventually default into open loop fuelling.

l

High CO reading.

l

Excess emissions.

l

Strong hydrogen sulphide (H

2

S) smell until the ECM defaults to open loop fuelling. .

l

MIL illuminated (NAS market only).

A number of diagnostic tests are performed by the ECM with regards to the HO

2

sensors:

l

HO

2

sensor and system diagnostics

l

HO

2

sensor heater diagnostics

l

HO

2

sensor switching period (ageing) diagnostics

l

Rear HO

2

sensor adaption diagnostic (NAS only)

l

Catalyst monitoring diagnostic

For further details of the heated oxygen sensors and exhaust emission control, refer to the V8 Emission Control
section of this manual.

+

EMISSION CONTROL - V8, DESCRIPTION AND OPERATION, Exhaust Emission Control System.

ENGINE MANAGEMENT SYSTEM - V8

18-2-32 DESCRIPTION AND OPERATION

Should a malfunction of the component occur the following fault codes may be evident and can be retrieved by
TestBook:

P Code

J2012 Description

Land Rover Description

P1129

O

2

sensors swapped bank to bank (sensor 1)

Front sensors transposed

P0130

O

2

sensor circuit malfunction (bank 1, sensor 1) Front sensor LH bank stoichiometric ratio outside

operating band

P0132

O

2

sensor circuit high voltage (bank 1, sensor 1) Front sensor LH bank short circuit to battery supply

P0134

O

2

sensor circuit no activity detected (bank 1,

sensor 1)

Front sensor LH bank open circuit

P0150

O

2

sensor circuit malfunction (bank 2, sensor 1) Front sensor RH bank stoichiometric ratio outside

operating band

P0152

O

2

sensor circuit high voltage (bank 2, sensor 1) Front sensor RH bank short circuit to battery supply

P0154

O

2

sensor circuit no activity detected (bank 2,

sensor 1)

Front sensor RH bank open circuit

P0136

O

2

sensor circuit malfunction (bank 1, sensor 2) Rear sensor LH bank stoichiometric ratio outside

operating band (NAS only)

P0137

O

2

sensor circuit low voltage (bank 1, sensor 2)

Rear sensor LH bank short circuit to earth (NAS only)

P0138

O

2

sensor circuit high voltage (bank 1, sensor 2) Rear sensor LH bank short circuit to battery supply

(NAS only)

P0140

O

2

sensor circuit no activity detected (bank 1,

sensor 2)

Rear sensor LH bank open circuit (NAS only)

P0156

O

2

sensor circuit malfunction (bank 2, sensor 2) Rear sensor RH bank stoichiometric ratio outside

operating band (NAS only)

P0157

O

2

sensor circuit low voltage (bank 2, sensor 2)

Rear sensor RH bank short circuit to earth (NAS only)

P0158

O

2

sensor circuit high voltage (bank 2, sensor 2) Rear sensor RH bank short circuit to battery voltage

(NAS only)

P0160

O

2

sensor circuit no activity detected (bank 2,

sensor 2)

Rear sensor RH bank open circuit (NAS only)

P0133

O

2

sensor circuit slow response (bank 1, sensor

1)

Front sensor aged - period time too long/too short LH
bank

P0153

O

2

sensor circuit slow response (bank 2, sensor

1)

Front sensor aged - period time too long/too short RH
bank

P1170

Downstream fuel trim malfunction (bank 1)

Front sensor aged - rear HO

2

S adaption too lean/too

rich LH bank (NAS and EU-3 only)

P1173

Downstream fuel trim malfunction (bank 2)

Front sensor aged - rear HO

2

S adaption too lean/too

rich RH bank (NAS and EU-3 only)

P0135

O

2

sensor heater circuit malfunction (bank 1,

sensor 1)

Front sensor heater LH bank - short/open circuit

P0141

O

2

sensor heater circuit malfunction (bank 1,

sensor 2)

Rear sensor heater LH bank - short/open circuit (NAS
and EU-3 only)

P0155

O

2

sensor heater circuit malfunction (bank 2,

sensor 1)

Front sensor heater RH bank - short/open circuit

P0161

O

2

sensor heater circuit malfunction (bank 2,

sensor 2)

Rear sensor heater RH bank - short/open circuit (NAS
and EU-3 only)

P0420

-

Catalyst efficiency deteriorated - LH bank (NAS and
EU-3 only)

P0430

-

Catalyst efficiency deteriorated - RH bank (NAS and
EU-3 only)