2010 ASTON MARTIN V8 VANTAGE Workshop Manual

AML EOBD System Operation Summary

Rory O’Curry Aston Martin Lagonda CONFIDENTIAL 1 May 2009
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Introduction


This document describes in detail the operation of the AML (Aston Martin Lagonda) EOBD System.

The AML EOBD System consists of a series of Mon itors designed to observe the operation of strategic
aspects of the Emission Control System. For each of the Monitors there is a detailed functional review of
the monitor's operation, a listing of the relevant malfunction codes, typical Monitor entry conditions
followed by typical malfunction thresholds.

The AML EOBD System also incorporates a Malfunction Indicator Lamp or MIL (symbol shown on the
last page). The MIL will only be used to report emi ssion related failures and to indicate emergency start-
up or Limp Home routines. It will not be used for any other purpose.

Although this document describes all the Monitors cont ained within the AML EOBD System, not ALL of
these monitors may be utilised on every vehicle built w ith the AML EOBD System. This is primarily due
to the hardware configuration of the particular vehicle in question e.g. Auto vs. Man Transmission OR
EGR vs. No EGR. Please refer to the vehicle specific documentation for details of those Monitors that will
be operational.

It is important to note that to illuminate the MIL, th e failure condition must be observed at least twice. The
first occurrence will set a 'pending code' and the second occurrence will illuminate the MIL. The only
exception to this is the Type A Misfire failure, whic h will 'flash' the MIL at the first occurrence of the
failure condition. Therefore, if an OBD reset is performed, a minimum of two trips is required to
illuminate the MIL, although the Misfire Monitor does require pre-conditioning to learn 'Profile
Correction' and will utilize three trips.

De-activation of the MIL can be achieved if, no furt her separate failure conditions are detected and 3
subsequent and sequential trips have been comp leted where the original failure condition which
illuminated the MIL initially, is no longer detected.

The MIL code will be completely erased if the same failure condition is not detected after 40 trips.

AML EOBD System Operation Summary

Rory O’Curry Aston Martin Lagonda CONFIDENTIAL 1 May 2009
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Catalyst Efficiency Monitor

The Catalyst Efficiency Monitor uses an oxygen sensor before and after the catalyst to infer Hydrocarbon
conversion efficiency, based on oxygen storage capac ity. Under normal closed-loop fuel conditions, high
efficiency catalysts have significant oxygen storage, which makes the switching frequency of the rear
HO2S quite slow compared with the switching freque ncy of the front HO2S. As catalyst efficiency
deteriorates, its ability to store oxygen declines and the post-catalyst HO2S signal begins to switch more
rapidly, approaching the switching frequency of the pre-catalyst HO2S.

In order to assess catalyst oxygen storage, the monitor compares front and rear HO2S signals during
closed-loop fuel conditions after the engine is warm ed-up and inferred catalyst temperature is within
limits. Front H02S signals are accumulated in up to ni ne different air mass regions or cells although 3 air
mass regions is typical. Rear H02S signals are counted in a single cell for all air mass regions. Currently
there are two algorithms that can be used to compare the front and rear HO2S signals:

1. Switch Ratio method;
The Switch Ratio method compares the 'switch frequencies' of the front and rear HO2S sensors. A
'switch' is counted every time the HO2S voltage output passes through a defined threshold (0.45 V).
The catalyst condition is diagnosed by dividing the number of rear H02S switches by the number of
front HO2S switches.

2. Index Ratio method.
The Index Ratio method calculates and compares the length of the front and rear HO2S signals. The
catalyst condition is diagnosed by dividing the length of the rear HO2S signal by the length of the front
HO2S signal.

A Switch / Index Ratio near 0.0 indicates high oxygen storage capacity, hence high HC efficiency. A
Switch / Index Ratio near 1.0 indicates low oxygen storage capacity, hence low efficiency. To improve the
robustness of the monitor, the Switch / Index Ratio is calculated using an Exponentially Weighted Moving
Average (EWMA) algorithm. If the Switch / Index Ratio exceeds the threshold, the catalyst is considered
failed.

AML EOBD System Operation Summary

Rory O’Curry Aston Martin Lagonda CONFIDENTIAL 1 May 2009
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Catalyst Monitor Operation:
DTCs P0420 Bank 1, P0430 Bank 2 for Series System ( and P0420 Complete
System for 'Y pipe' configuration ).
Monitor execution once per driving cycle
Monitor Sequence HO2S monitor complete and OK
Sensors OK ECT, IAT, TP, VSS, CPS
Monitoring Duration Approximately 900 seconds dur ing appropriate conditions (approximately
200 to 600 oxygen sensor switches are collected).

Typical catalyst monitor entry conditions: Minimum Maximum
Time since engine start-up (70 oF start) 240 seconds
Engine Coolant Temp 160 oF 230 oF
Intake Air Temp 20 oF 180 oF
Engine Load 10%
Throttle Position Part Throttle Part Throttle
Time since entering closed loop fuel 30 sec
Vehicle Speed 5 mph 70 mph
Steady Air Mass Flow 1.0 lb/min 5.0 lb/min
( Note: 25 - 35 mph steady state driving must be performed to complete the monitor )

Typical malfunction thresholds:
Rear-to-front O2 sensor switch-ratio/ Index Ratio > 0.75

Catalyst Monitor temporary disablement conditions (other than entry requirements) :
EGR, Secondary air, Front and Rear O2 sensor, Engine Coolant Temperature, Mass Air Flow sensor, Air
Charge Temperature sensor, Profile Ignition Pickup & Throttle Position monitor failure.

AML EOBD System Operation Summary

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Misfire Monitor

Neural Network Misfire detection is used in order to achieve "full-range" capability. All software allows
for detection of any misfires that occur 6 engine revolutions after initially cranking the engine. This
meets the new OBD-II requirement to identify misfires within 2 engine revolutions after exceeding the
warm drive, idle rpm.
.

Neural Network System

The Neural Net Misfire (NNM) monitor uses a dedicated microprocessor in the PCM along with
crankshaft position, (36–tooth wheel), camshaft position, and engine load to determine engine misfire. A
neural network is different way of computing that uses a large number of simple processing elements with
a high degree of interconnection to process complex inform ation. It is based on the parallel architecture of
the brain. The processing elements have adaptive ch aracteristics (coefficients) that must be learned
through a process called training. During training, the netw ork is fed a sample set of data that consists of
the inputs along with the desired output (e.g. misfire/no misfire). The network coefficients are recursively
optimized so that the correct output is generated fro m the set of inputs and error is minimized. Once the
coefficients have been learned, the network can process "real" data.

AML EOBD System Operation Summary

Rory O’Curry Aston Martin Lagonda CONFIDENTIAL 1 May 2009

Misfire Monitor (continued)


NNM uses a Motorola Star 12 microprocessor in the PCM to perform the NNM calculations. The
Motorola Star 12 is used in all markets for the Ast on Martin application. The neural network size is 23
nodes and 469 coefficients.
Inputs to Neural Net
• Crankshaft acceleration from the crank position (CKP) sensor
• RPM (calculated from CKP)
• LOAD (normalized for air mass and rpm)
• Indication of cam position from camshaft position (CMP) sensor
Output from Neural Net
• Misfire Call: - 0 (indicating no misfire) or 1 (indicating misfire)

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NNM System Hardware Design


PCM MIL


















Generic Misfire Algorithm Processing.


The acceleration that a piston undergoes during a normal firing event is directly related to the amount of
torque that cylinder produces. The calculated piston/cylinder acceleration value(s) are compared to a
misfire threshold that is continuously adjusted based on inferred engine torque. Deviant accelerations
exceeding the threshold are conditionally labeled as misfires.

The calculated deviant acceleration value(s) are also evaluated for noise. Normally, misfire results in a
non-symmetrical loss of cylinder acceleration. Mechan ical noise, such as rough roads or high rpm/light
load conditions, will produce symmetrical acceleration va riations. Cylinder events that indicate excessive
MAF Signal
CKP Signal
Main PPC
Processor
HCS12HCS12LOAD_FG
CKP Signal
Misfire calls, or
Δt’s
Misfire fault counters
Status Flags
CID Signal
Misfire disablements
Profile Learning CKP
-> ACCEL, RPM
CID -> local sync
Signal validation
Profile application
Executes Neural Net
CID Signal

AML EOBD System Operation Summary

Rory O’Curry Aston Martin Lagonda CONFIDENTIAL 1 May 2009
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deviant accelerations of this type are considered noise. Noise-free deviant acceleration exceeding a given
threshold is labeled a misfire.

The number of misfires are counted over a continuous 200 revolution and 1000 (or 4000)
revolution period. (The revolution counters are not reset if the misfire monitor is temporarily disabled such
as for negative torque mode, etc.) At the end of the evaluation period, the total misfire rate and the misfire
rate for each individual cylinder is computed. The misfire rate evaluated every 200 revolution period
(Type A) and compared to a threshold value obtaine d from an engine speed/load table. This misfire
threshold is designed to prevent damage to the cat alyst due to sustained excessive temperature. If the
misfire threshold is exceeded and the catalyst temperature model calculates a catalyst mid-bed temperature
that exceeds the catalyst damage threshold, the MIL blinks at a 1 Hz rate while the misfire is present. If the
threshold is again exceeded on a subsequent driving cy cle, the MIL is illuminated. If a single cylinder is
indicated to be consistently misfiring in excess of the catalyst damage criteria, the fuel injector to that
cylinder may be shut off for a period of time to pr event catalyst damage. Up to two cylinders may be
disabled at the same time. This fuel shut-off feature is used on many 8-cylinder engines. It is never used
on a 4-cylinder or 6-cylinder engine. Next, the misf ire rate is evaluated every 1000 (or 4000) rev period
and compared to a single ( Type B ) threshold value to indicate an emission-threshold malfunction. If a
1000 rev period is calibrated, a single 1000 rev exceedence from startup or four subsequent 1000 rev
exceedences on a drive cycle after start-up is used as the malfunction criteria. If a 4000 rev period is
calibrated, a single 4000 rev exceedence is used to indicate an emission-threshold malfunction.





Misfire Monitor Operation :
DTCs P0300 to P0312, P316 ,P1309, P1310, P1311
Monitor execution Continuous, misfire rate calculated every 200 and 1000 or 4000 revs
Monitor Sequence none
Sensors OK CKP, CMP, ECT
Monitoring Duration Entire driving cycle ( see disablement conditions below )

Typical misfire monitor entry conditions Minimum Maximum
Time since engine start-up 5 seconds
Engine Coolant Temp 20 oF 250 oF
RPM Range idle as per Directive
Profile correction factors learned in KAM Yes

Misfire Monitor temporary disablement conditions ( other than entry requirements )
Closed throttle decels (negative torque, engine being driven)
Engine Torque Reduction Modes
Accessory load-state change (A/C, power steering)
EGR Monitor Flow Test

Typical misfire monitor malfunction thresholds :
Type A (catalyst damaging misfire rate) misfire rate is an rpm/load table ranging from 40% at idle to
4% at high rpm and loads.
Type B (emission threshold rate) 1% to 5%

AML EOBD System Operation Summary

Rory O’Curry Aston Martin Lagonda CONFIDENTIAL 1 May 2009
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Fuel System Monitor

As fuel system components age or otherwise change over the life of the vehicle, the adaptive fuel strategy
learns deviations from stoichiometry while running in closed loop fuel. These learned corrections are
stored in Keep Alive Memory as long term fuel tr im corrections. They may be stored into an 8x10
rpm/load table or they may be stored as a function of air mass. As components continue to change beyond
normal limits or if a malfunction occurs, the long term fuel trim values will reach a calibratable rich or
lean limit where the adaptive fuel strategy is no longe r allowed to compensate for additional fuel system
changes. Long term fuel trim corrections at their limits, in conjunction with a calibratable deviation in
short term fuel trim, indicate a rich or lean fuel system malfunction.


Fuel Monitor Operation:
DTCs P0171 Bank 1 Lean, P0174 Bank 2 Lean
P0172 Bank 1 Rich, P0175 Bank 2 Rich
Monitor execution continuous while in closed loop fuel
Monitor Sequence none
Monitoring Duration 2 seconds to register malfunction

Typical fuel monitor entry conditions Minimum Maximum
RPM Range idle 4,000 rpm
Air Mass Range 0.75 lb/min 8.0 lb/min
Purge Duty Cycle 0% 0%

Typical fuel monitor malfunction thresholds:
Long Term Fuel Trim correction cell currently being utilized in conjunction with Short Term Fuel Trim:
Lean malfunction: LTFT > 25%, STFT > 5%
Rich malfunction: LTFT < 25%, STFT < 10%

Fuel Monitor temporary disablement conditions ( other than entry requirements ) :
None.

AML EOBD System Operation Summary

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HO2S Monitor

Front HO2S Signal

The time between HO2S switches is monitored after vehicle startup and during closed loop fuel
conditions. Excessive time between switches or no switc hes since startup indicate a malfunction. Since
'lack of switching' malfunctions can be caused by HO2S sensor malfunctions or by shifts in the fuel
system, DTCs are stored that provide additional information for the 'lack of switching' malfunction.
Different DTCs indicate whether the sensor was st uck lean/disconnected (P1131, P1151), stuck rich
(P1132, P1152) or stopped switching due to excessive long term fuel trim corrections (P1130, P1150).

HO2S 'Lack of Switching' Operation:
DTCs Bank 1 – P0132, P2195, P2196
Bank 2 – P0152, P2197, P2198
Monitor execution continuous, from startup and while in closed loop fuel
Monitor Sequence none
Sensors OK TP, MAF, MAP, ECT, CHT, ACT, IAT
Monitoring Duration 30 to 60 seconds to register a malfunction

Typical HO2S 'Lack of Switching' entry conditions : Minimum Maximum
Throttle Position part throttle
Idle State (not at idle, part throttle)
Engine Load 20% 60%
Time since engine start-up 180 seconds
Inferred Exhaust Temperature 800 oF

Typical HO2S 'Lack of Switching' malfunction thresholds:
< 5 switches since startup after 30 seconds in test conditions
> 60 seconds since last switch while closed loop
> 30 seconds since last switch while closed loop at Short Term Fuel Trim limit

HO2S lack of switching temporary disablement conditions (other than entry requirements) :
Air Charge Temperature, ACT (or IAT) < -20 °F (minimum Cold Climate Test Temperature).
Failure of the sensors mentioned in the above “Sensors OK” section.

The HO2S is also tested functionally. The response rate is evaluated by enteri ng a fixed frequency square
wave, fuel control routine. This routine drives the air/fuel ratio around stoichiometry at a calibratable
frequency and magnitude, producing pr edictable oxygen sensor signal amplitude. A slow sensor will show
a reduced amplitude. Oxygen sensor signal amplitude below a minimum threshold indicates a slow sensor
malfunction (P0133 Bank 1, P0153 Bank 2).

HO2S Response Rate Operation:
DTCs Bank 1 - P0133, Bank 2 - P0153
Monitor execution once per driving cycle
Monitor Sequence none
Sensors OK ECT, IAT, MAF, MAP, VSS, CKP, TP, CMP, no misfire DTCs
Monitoring Duration 4 seconds