1999 LAND ROVER DISCOVERY check engine

EMISSION CONTROL - V8
DESCRIPTION AND OPERATION 17-2-43
Secondary Air Injection System
Operation
When the engine is started, the engine control module checks the engine coolant temperature and if it is below 55°
C, the ECM grounds the electrical connection to the coil of the secondary air injection (SAI) pump relay.
A 12V battery supply is fed to the inertia switch via fuse 13 in the engine compartment fusebox. When the inertia
switch contacts are closed, the feed passes through the switch and is connected to the coil of the Main relay. An earth
connection from the Main relay coil is connected to the ECM. When the ECM completes the earth path, the coil
energises and closes the contacts of the Main relay.
The Main and Secondary Air Injection (SAI) pump relays are located in the engine compartment fusebox. When the
contacts of the Main relay are closed, a 12V battery supply is fed to the coil of the SAI pump relay. An earth connection
from the coil of the SAI pump relay is connected to the ECM. When the ECM completes the earth path, the coil
energises and closes the contacts of the SAI pump relay to supply 12V to the SAI pump via fusible link 2 in the engine
compartment fusebox. The SAI pump starts to operate, and will continue to do so until the ECM switches off the earth
connection to the coil of the SAI pump relay.
The SAI pump remains operational for a period determined by the ECM and depends on the starting temperature of
the engine, or for a maximum operation period determined by the ECM if the target engine coolant temperature has
not been reached in the usual time.
When the contacts of the main relay are closed, a 12V battery supply is fed to the SAI solenoid valve via Fuse 2 in
the engine compartment fusebox.
The ECM grounds the electrical connection to the SAI vacuum solenoid valve at the same time as it switches on the
SAI pump motor. When the SAI vacuum solenoid valve is energised, a vacuum is provided to the operation control
ports on both of the vacuum operated SAI control valves at the exhaust manifolds. The control vacuum is sourced
from the intake manifold depression and routed to the SAI control valves via a vacuum reservoir and the SAI vacuum
solenoid valve.
The vacuum reservoir is included in the vacuum supply circuit to prevent vacuum fluctuations caused by changes in
the intake manifold depression affecting the operation of the SAI control valves.
When a vacuum is applied to the control ports of the SAI control valves, the valves open to allow pressurised air from
the SAI pump to pass through to the exhaust ports in the cylinder heads for combustion.
When the ECM has determined that the SAI pump has operated for the desired duration, it switches off the earth paths
to the SAI pump relay and the SAI vacuum solenoid valve. With the SAI vacuum solenoid valve de-energised, the
valve closes, cutting off the vacuum supply to the SAI control valves. The SAI control valves close immediately and
completely to prevent any further pressurised air from the SAI pump entering the exhaust manifolds.
The engine coolant temperature sensor incurs a time lag in respect of detecting a change in temperature and the SAI
pump automatically enters a 'soak period' between operations to prevent the SAI pump overheating. The ECM also
compares the switch off and start up temperatures, to determine whether it is necessary to operate the SAI pump.
This prevents the pump running repeatedly and overheating on repeat starts.
Other factors which may prevent or stop SAI pump operation include the prevailing engine speed / load conditions.

EMISSION CONTROL - V8
17-2-44 DESCRIPTION AND OPERATION
SAI System Fault Finding and Check
Malfunctions
The SAI system diagnostics monitor the whole SAI system for correct operation. Malfunction of any one of the SAI
system components can cause fault codes to be stored in the ECM diagnostic memory.
Correct fault finding methods and investigation are essential to determine the root cause of the generated fault code(s)
and prevent mis-diagnosis.
NOTE: TestBook/T4 must be used to perform active SAI diagnostics.
Fault Finding
In the event of SAI system malfunction and P Codes 1412 – 1417 being stored in the ECM diagnostic memory, the
following information is designed to provide a logical checking process for investigation of the root cause(s) of the
fault. This fault finding guide should be used in conjunction with the following 'Checking Malfunctions' procedure and
other information contained in this Emissions section.
It is important that these procedures are performed to prevent the following:
lExcessive instances of No Fault Found (NFF) components in warranty returns
lMultiple repeat complaints from the customer before the cause of the fault is found.
The following table lists the P codes applicable to the SAI system and their meaning:
Passive Test (P Codes 1412 and 1415)
During normal SAI operation the ECM uses HO2S sensor voltage output to determine if sufficient flow is being
introduced into the exhaust system. Depending on which banks of the engine detect the fault, one or both P codes
can be stored.
Active Tests
If the normal operation of the passive SAI diagnostics cannot be completed, (SAI operation being suspended by load/
speed conditions, for instance) the ECM will attempt to perform an 'Active' test of the system when conditions allow.
These conditions include, but are not limited to: 'Engine fully warm' and 'Engine at idle'. The active test comprises two
parts; a 'Leak Test' followed by a 'Flow Test'.
Leak Test (P Codes P1413 and P1416)
The SAI pump is operated without opening the SAI control valves. In this condition no SAI flow should enter the
exhaust system. By monitoring the HO2S sensor voltage output, the ECM determines if the system is functioning
correctly. Depending on which bank of the engine detects the fault, one or both P codes can be stored.
P-code Description
P1412Secondary Air Injection System – Malfunction Bank 1 LH (Insufficient SAI flow
during passive test)
P1413Secondary Air Injection System – Air control valve always open Bank 1 LH
(Excessive SAI flow during active leak test)
P1414Secondary Air Injection System – Malfunction Bank 1 LH (Insufficient SAI flow
during passive test)
P1415Secondary Air Injection System – Malfunction Bank 2 RH (Insufficient SAI flow
during passive test)
P1416Secondary Air Injection System – Ait control valve always open Bank 2 RH
(Excessive SAI flow during active leak test)
P1417Secondary Air Injection System – Low air flow Bank 2 RH (Insufficient SAI flow
during active test)

EMISSION CONTROL - V8
DESCRIPTION AND OPERATION 17-2-45
Flow Test (P Codes P1414 and P1417)
When the Leak test has been passed successfully, the SAI control valves are then opened while the SAI pump is still
operational. Flow should now begin to enter the exhaust system. By monitoring the HO2S sensor voltage output, the
ECM determines if sufficient flow is being introduced into the exhaust system. Depending on which bank of the engine
detects the fault, one or both P codes can be stored.
Fault Finding Methodology
Malfunctions can be broadly categorised into two different categories: Flow Faults or Leak Faults.
Additionally, they also differ depending if the corresponding P code exists for both cylinder banks simultaneously or
is unique to one bank, for example:
Faults of each of the four basic types should be investigated in a different priority order, starting with the most logically
plausible cause or component.
Fault Finding Flow Charts
The following flow charts show the order of investigation that should be performed depending on the type of fault
present. These should be treated as guidelines to ensure that the most likely and plausible causes are addressed first.
However, the flow charts assume that no clear or obvious reason for failure exists. If the cause of the malfunction is
immediately obvious, then the flow charts should not be followed.
Once a malfunction is identified, it should be rectified as necessary and the system checked as per the instructions
in the following 'Checking Malfunctions' section.
NOTE: It is not necessary to follow the remainder of the flow chart once a potential root cause has been identified.
Flow Fault Finding chart
1Fault codes P1412, P1414, P1415 or P1417 present
2Insufficient flow detected
3Is fault present on both cylinder banks?
If 'NO' proceed to step 4
If 'YES' proceed to step 8
4Vacuum supply – Check for: blockage and/or vacuum line disconnected from SAI valve
5SAI Valve – Check for: jam / diaphragm leak or blockage
6Delivery Hoses to SAI Valve – Check for: blockage / leaks
7SAI Pipes to Cylinder Head – Check for: blockage / leaks
8Electrical Issue – Check for: Related P code (relay/fuse/solenoid), rectify as necessary and check connectors
9Vacuum Supply – Check for: Blocked/leaking vacuum lines or correct solenoid operation (open/closed)
10Delivery Hoses – Check for: Blocked/leaking hoses
11SAI Pump – Check for: Correct operation using TestBook/T4 or pump blockage/failure
12SAI Valves – Check for: Both SAI Valves jammed/blocked/leaking diaphragms
Leak Fault Finding Chart
1Fault codes P1413 or P1416 present
2SAI system leak detected
3Is fault present on both cylinder banks?
If 'NO' proceed to step 4
If 'YES' proceed to step 5
4SAI Valve – Check for: leakage
5Vacuum supply – Check for: solenoid stuck open (mechanical failure) or stuck open (electrical failure)
6SAI Valve – Check for: leakage from one or both valves
P Code Type One Bank Only Both Banks
FlowIII
LeakIII IV

EMISSION CONTROL - V8
DESCRIPTION AND OPERATION 17-2-47
The following table shows the components itemised on the above illustration and the test applicable to each
component.
Test 1– Secondary Air Injection (SAI) Pump
Power Supply and Relay
Check all wiring and connections.
Functional Check of SAI Pump
The ECM checks the engine coolant temperature when the engine is started in addition to checking the elapsed time
since the last engine start. The engine coolant temperature must be below 55°C (131°F) and the ambient temperature
above 8°C (46°F) for the SAI pump to run. Also, depending on the long term 'modelled' ambient temperature
determined by the ECM, the minimum time elapsed required since the last engine start can be up to 8.25 hours. The
period of time that the SAI pump runs for depends on the starting temperature of the engine and varies from
approximately 95 seconds for a start at 8°C (46°F) to 30 seconds for a start at 55°C (131°F).
With a warm engine which is switched off and the SAI pump relay removed, the SAI pump can be supplied with power
by bridging terminals 87 and 30 at the relay socket.
CAUTION: Ensure that terminals 87 and 87a are not connected or bridged in any way, a short circuit will
occur.
NOTE: TestBook/T4 can also be used to force the SAI system to perform an SAI active diagnostic routine. During this
routine the SAI pump will run for approximately 10 seconds.
When the terminals are bridged or the diagnostic routine initiated, the pump must run when requested which will be
noticeable by the running noise of the pump. Only allow the SAI pump to run for a maximum of 90 seconds and allow
sufficient time for the pump to cool down before running again.
If the SAI pump does not run or makes a scraping noise, it must be replaced. In this case, all other system components
must also be checked.
Noise Complaints
If the SAI pump runs but the operating noise is excessively loud, the external components of the pump, cable, hose
line, and decoupling segments, must be checked. Check the decoupling segments and hose line for distortion and
the cable and hose line for contact with the pump body.
If excessive noise still occurs, the SAI pump must be replaced.
NOTE: Before a new SAI pump is fitted, the SAI control valves must checked for correct function and tightness – Refer
to Test 2 – Secondary Air Injection (SAI) Control Valves.
When fitting a new SAI pump, ensure that the hose lines, the cable and the decoupling segments are fitted without
tension and contact with the pump body.
Item No. Component Description Applicable Test
1 SAI Pump Test 1 – Secondary Air Injection (SAI) Pump
2 SAI control valves (1 per engine bank) Test 2 – Secondary Air Injection (SAI) Control
Valves
3 Vacuum solenoid valve Test 3 – Vacuum Solenoid Valve
4 Delivery hoses to SAI control valves Test 4 – Delivery Hoses to Secondary air
Injection (SAI) Control Valves
5 Connection to air manifold (SAI rail) Test 5 – Connection to Air Manifold
6 Vacuum line (intake manifold to vacuum solenoid valve) Test 6 – Vacuum Lines
7 Vacuum lines (vacuum solenoid valve to SAI control valves) Test 6 – Vacuum Lines

EMISSION CONTROL - V8
DESCRIPTION AND OPERATION 17-2-49
Test 3 – Vacuum Solenoid Valve
Function
The vacuum solenoid valve is energised for the duration of the secondary air injection. The valve is open when
energised, the intake manifold vacuum acts on the diaphragm of the SAI control valve and the control valve opens.
The solenoid valve is closed when de-energised.
Power Supply
Remove the harness connector from the vacuum solenoid valve and check the voltage between the connection
terminals. No voltage must be present at the connector after switching off the SAI pump.
Opening/Tightness
Disconnect the vacuum line at one of the SAI control valves and connect a hand vacuum pump to the line. With the
engine running at idle, a pressure difference of a minimum of 390 mbar (5.65 lbf/in
2) must measurable on the hand
vacuum pump gauge with the vacuum solenoid valve energised.
The vacuum solenoid valve must be sealed when de-energised. If the Opening/tightness test fails, replace the
vacuum solenoid valv.
Test 4 – Delivery Hoses to Secondary air Injection (SAI) Control Valves
Visually inspect the delivery hoses to the SAI control valves for damage or blockage. If damage, condensate or
deposits are found the delivery hoses must be replaced. Check the hoses for correct connection and leaks.
Test 5 – Connection to Air Manifold
Check the connection for leaks visually or by using a leak detection spray. Reseal the connection if necessary.
Test 6 – Vacuum Lines
Visually inspect the vacuum lines for damage. Check each line for leaks or blockages using the vacuum hand pump.
Check the lines for correct connection.

ENGINE MANAGEMENT SYSTEM - V8
18-2-20 DESCRIPTION AND OPERATION
There are three types of ECT sensor diagnostic checks:
lThe ECT sensor signal is within limits, but is inaccurate – the engine has to be running and the signal indicates
a coolant temperature below 40°C (104°F). The signal differs too much from the coolant temperature model for
longer than 2.53 seconds.
lThe ECT sensor signal is greater than the maximum threshold value – the ECM has to be powered up to perform
the diagnostic, but the engine does not need to be running.
lThe ECT sensor signal is less than the minimum threshold value – the ECM has to be powered up to perform
the diagnostic, but the engine does not need to be running.
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
P0116 Engine coolant temperature circuit/range
performance problemSignal differs too much from temperature model for
longer than 2.53s
P0117 Engine coolant temperature circuit low input Open circuit or short circuit to battery supply
P0118 Engine coolant temperature circuit high input Short circuit to earth

ENGINE MANAGEMENT SYSTEM - V8
18-2-22 DESCRIPTION AND OPERATION
Input/Output
The ECM provides the thermostat monitoring sensor with a 5 volt reference via pin 21 of connector C0635 of the ECM,
and an earth via pin 5 of connector C0635 of the ECM.
There are three types of thermostat monitoring sensor diagnostic checks:
lSensor signal is above maximum threshold. For the ECM to register this as a fault, and illuminate the MIL, the
temperature registered by the thermostat monitoring sensor must be above 140 °C (284 °F) for more than 1
second.
lSensor signal is below minimum threshold. For the ECM to register this as a fault, and illuminate the MIL, the
temperature registered by the thermostat monitoring sensor must be below -33 °C (-27 °F) for more than 1
second, while the inlet air temperature reading is greater than -32 °C (-25 °F).
lSignal difference between ECT sensor and thermostat monitoring sensor is below maximum threshold. For the
ECM to register this as a fault, and illuminate the MIL, the following conditions must exist:
lNo maximum or minimum threshold signal faults exist.
lNo faults are recorded against the thermostat monitoring sensor or vehicle speed signal.
lEngine not in idle speed control.
lFuel cut-off not active.
lEngine speed is greater than 400 rpm.
lRoad speed is greater than 0 mph.
lIntegrated mass air flow from engine start to fuel cut-off is greater than set value (between 3 kg and 10 kg
dependent upon engine coolant temperature at engine start).
lEngine coolant temperature at engine start is between 9 °C and 39 °C (48 °F and 102 °F).
lHigh range is selected.
lDelay time before thermostat monitoring is enabled is between set limits (between 50 and 500 seconds
dependent upon engine coolant temperature at engine start).
lEngine coolant temperature is greater than 90 °C (194 °F).
lThe difference between the ECT sensor reading and the thermostat monitoring sensor reading is less than
39 °C (102 °F).

ENGINE MANAGEMENT SYSTEM - V8
DESCRIPTION AND OPERATION 18-2-25
In the event of a MAF sensor signal failure any of the following symptoms may be observed:
lDuring driving engine rev/min may dip, before recovering.
lDifficult starting.
lEngine stalls after starting.
lDelayed throttle response.
lEmissions control inoperative.
lIdle speed control inoperative.
lReduced engine performance.
lMAF sensor signal offset.
There are two types of MAF sensor diagnostic check:
lThe MAF sensor signal is less than the minimum threshold for specific speed range – the engine must have
exceeded 200 rev/min for longer than 300 ms and remain above 400 rev/min. The signal must be less than the
threshold mapped against engine speed for longer than 500 ms.
lThe MAF sensor signal is greater than the maximum threshold for specific speed range – the engine must have
exceeded 200 rev/min for longer than 10 ms. The signal must be greater than the threshold mapped against
engine speed for longer than 300 ms.
If the MAF sensor fails the following fault codes will be produced and can be retrieved by TestBook:
P code J2012 description Land Rover description
P0102 Mass or volume air flow low input MAF signal < minimum threshold, which is speed
dependent
P0103 Mass or volume air flow circuit high input MAF signal > maximum threshold, which is speed
dependent