Aston Martin diagnostic trouble code
P0174: System Too Lean (Bank 2)
Use this reference to understand the recorded condition, confirm the available V8 Vantage or DB9 manual coverage, and follow the documented diagnostic checks before replacing parts.
- Code family
- Powertrain
- Vehicle system
- Other vehicle system
- Manual coverage
- V8 Vantage, DB9
- Warning-lamp status
- V8 Vantage: MIL; DB9: MIL
What Aston Martin code P0174 means
System Too Lean (Bank 2)
DB9 preliminary diagnostic manual · section 2-44
Manufacturer fault-analysis procedure
Manual fault definition
P0171 - HO2S1-1 Fuel/air ratio too lean
P0174 - HO2S2-1 Fuel/air ratio too lean
Adaptive fuel correction at the limit.
P0174 - HO2S2-1 Fuel/air ratio too lean
Adaptive fuel correction at the limit.
Cautions and notes
CAUTION: These code may be generated in the
Primary or Secondary Powertrain Control Module
(PCM) Check that you are working on the correct
half of the engine.
Primary or Secondary Powertrain Control Module
(PCM) Check that you are working on the correct
half of the engine.
Test sequence and decision path
1. Verify that the vehicle did not run out of fuel
before the Check Engine light came on.
If a ‘No Fuel’ condition has been present, connect the WDS or scan tool and clear the P0171/
P0174 code. Perform the KOER test sequence to
check that the fuel adaption is now functioning
correctly.
If the vehicle has not recently run out of fuel, analyse the problem using the following procedure.
2. Carry out a thorough visual inspection of the
vehicle, concentrating on the following possible
causes of the lean mixture:
Fuel System
Leaking fuel injectors
Low fuel pressure
Blocked fuel injectors
Damaged/disconnected HO2S circuits
Induction System
Air leaks after the air flow meter
Vacuum leaks
Restricted air inlet
Fuel Vapour Purge System
Positive Crankcase Ventilation system
Base Engine
Oil overfill
Cam timing
Compression pressure
Ignition System
Ignition coil windings
Ignition coil connection
Spark plugs
Repair any problems identified in the visual
inspection, clear the P0171/P0174 fault code and
repeat the KOER Test. If the code is detected
again, proceed as follows.
3. If any adaptive fuel codes are detected in step 2,
go to step 4. For other codes, go to the appropriate procedure in this section of the fault analysis
manual.
4. Check the fuel pressure as follows:
Connect the WDS and set datalogger to monitor
the fuel pressure sensor output from both fuel
rails.
Start the engine and run at idle speed.
Increase the engine speed to 2500 rpm and maintain for 1 minute.
Note the recorded fuel pressure at idle and at
2500 rpm. The fuel system must be capable of
maintaining at least 40 psi above manifold pressure.
If the fuel pressure is low, repair or service the
fuel system to meet fuel pressure specification.
5. Check the fuel system ability to hold fuel pressure.
Cycle the ignition key on and off several times.
Verify that there are no external fuel leaks (repair
as necessary)
6. Key off. Disconnect the fuel injector electrical
connectors. Check the resistance of the fuel injectors.
Each resistance should be in the range 11 - 18
Ω
If all injector resistance values are in range, consult Aston Martin technical Support.
If any injector resistance is out of range, replace
the injector.
Reconnect all injectors. Clear the P0171/P0174
codes and run a KOER test to ensure that the
problem is resolved.
Figure 3. Fuel Injector Circuits
BU,0.5
BY,0.5
BK,0.5
BW,0.5
BS,0.5
BR,0.5
KB,0.5
WB,0.5
RB,0.5
SB,0.5
UB,0.5
KB,0.5
NY,0.5
NY,0.5
NY,0.5
NY,0.5
NY,0.5
NY,0.5
NY,0.5
NY,0.5
NY,0.5
NY,0.5
NY,0.5
NY,0.5
NY,0.5
NY,0.5
Conn-ECU B (E-Engine)
Injector 12
Underbonnet Fusebox
Module
Central Electronic
Sheet 61
Sheet 61
C2409-1
DIODE 4
RELAY 3
DIODE 5
RELAY 5
F54
10.0 Amps
F13
20.0 Amps
F9
20.0 Amps
12 Ohms
12 Ohms
12 Ohms
12 Ohms
12 Ohms
12 Ohms
Injector 8
Injector 7
Injector 9
Injector 11
Injector 10
12 Ohms
12 Ohms
12 Ohms
12 Ohms
12 Ohms
12 Ohms
Injector 1
Injector 2
Injector 3
Injector 4
Injector 5
Injector 6
Conn-ECU A (E-Engine)
C0584-39
IGN. OUT
C0574-6 GND
C2608-1 VBATT
C0579-8 VIGN
SPL5-VIGN/EN
C0578-2
C0577-6
SPL2-VIGN/EN
C0529-2
C0528-2
C2456-2
C2459-2
C2458-2
C2457-2
C0529-1
C0528-1
C2456-1
C2459-1
C2458-1
C2457-1
C0522-2
C0523-2
C0524-2
C0525-2
C0526-2
C0527-2
C0522-1
C0523-1
C0524-1
C0525-1
C0526-1
C0527-1
C2464-2G INJ7
C2464-8G INJ11
C2464-9G INJ8
C2464-3G INJ12
C2464-4G INJ10
C2464-5G INJ9
C0636-2G INJ1
C0636-8G INJ5
C0636-5G INJ3
C0636-9G INJ2
C0636-4G INJ4
C0636-3G INJ6
See Power Distribution
7. Check for codes P0201 - P0206 (injector faults)
and analyse these codes if present. Return to step
9 of this procedure if either P0171 or P0174 are
logged again after clearing the P0201 - P0206
codes.
8. Flow test the injectors:
Use a Rotunda Injector Tester or equivalent to
flow test the injectors according to the manufacturers instructions.
If any injector flow rate is not within specification,
replace the defective injector. Refit the injectors
and rerun the KOER Test.
If the injector flow rates are all within specification, the problem is not fuel related.
9. Check the cylinder compression pressures using
the service manual procedure.
If any compression pressure is low, repair the engine as necessary.
If the compression pressures are in specification,
carry out further analysis as for DTC P1131 to
check the heated oxygen sensors and circuits.
Open the corresponding manual page for wiring diagrams and figures
before the Check Engine light came on.
If a ‘No Fuel’ condition has been present, connect the WDS or scan tool and clear the P0171/
P0174 code. Perform the KOER test sequence to
check that the fuel adaption is now functioning
correctly.
If the vehicle has not recently run out of fuel, analyse the problem using the following procedure.
2. Carry out a thorough visual inspection of the
vehicle, concentrating on the following possible
causes of the lean mixture:
Fuel System
Leaking fuel injectors
Low fuel pressure
Blocked fuel injectors
Damaged/disconnected HO2S circuits
Induction System
Air leaks after the air flow meter
Vacuum leaks
Restricted air inlet
Fuel Vapour Purge System
Positive Crankcase Ventilation system
Base Engine
Oil overfill
Cam timing
Compression pressure
Ignition System
Ignition coil windings
Ignition coil connection
Spark plugs
Repair any problems identified in the visual
inspection, clear the P0171/P0174 fault code and
repeat the KOER Test. If the code is detected
again, proceed as follows.
3. If any adaptive fuel codes are detected in step 2,
go to step 4. For other codes, go to the appropriate procedure in this section of the fault analysis
manual.
4. Check the fuel pressure as follows:
Connect the WDS and set datalogger to monitor
the fuel pressure sensor output from both fuel
rails.
Start the engine and run at idle speed.
Increase the engine speed to 2500 rpm and maintain for 1 minute.
Note the recorded fuel pressure at idle and at
2500 rpm. The fuel system must be capable of
maintaining at least 40 psi above manifold pressure.
If the fuel pressure is low, repair or service the
fuel system to meet fuel pressure specification.
5. Check the fuel system ability to hold fuel pressure.
Cycle the ignition key on and off several times.
Verify that there are no external fuel leaks (repair
as necessary)
6. Key off. Disconnect the fuel injector electrical
connectors. Check the resistance of the fuel injectors.
Each resistance should be in the range 11 - 18
Ω
If all injector resistance values are in range, consult Aston Martin technical Support.
If any injector resistance is out of range, replace
the injector.
Reconnect all injectors. Clear the P0171/P0174
codes and run a KOER test to ensure that the
problem is resolved.
Figure 3. Fuel Injector Circuits
BU,0.5
BY,0.5
BK,0.5
BW,0.5
BS,0.5
BR,0.5
KB,0.5
WB,0.5
RB,0.5
SB,0.5
UB,0.5
KB,0.5
NY,0.5
NY,0.5
NY,0.5
NY,0.5
NY,0.5
NY,0.5
NY,0.5
NY,0.5
NY,0.5
NY,0.5
NY,0.5
NY,0.5
NY,0.5
NY,0.5
Conn-ECU B (E-Engine)
Injector 12
Underbonnet Fusebox
Module
Central Electronic
Sheet 61
Sheet 61
C2409-1
DIODE 4
RELAY 3
DIODE 5
RELAY 5
F54
10.0 Amps
F13
20.0 Amps
F9
20.0 Amps
12 Ohms
12 Ohms
12 Ohms
12 Ohms
12 Ohms
12 Ohms
Injector 8
Injector 7
Injector 9
Injector 11
Injector 10
12 Ohms
12 Ohms
12 Ohms
12 Ohms
12 Ohms
12 Ohms
Injector 1
Injector 2
Injector 3
Injector 4
Injector 5
Injector 6
Conn-ECU A (E-Engine)
C0584-39
IGN. OUT
C0574-6 GND
C2608-1 VBATT
C0579-8 VIGN
SPL5-VIGN/EN
C0578-2
C0577-6
SPL2-VIGN/EN
C0529-2
C0528-2
C2456-2
C2459-2
C2458-2
C2457-2
C0529-1
C0528-1
C2456-1
C2459-1
C2458-1
C2457-1
C0522-2
C0523-2
C0524-2
C0525-2
C0526-2
C0527-2
C0522-1
C0523-1
C0524-1
C0525-1
C0526-1
C0527-1
C2464-2G INJ7
C2464-8G INJ11
C2464-9G INJ8
C2464-3G INJ12
C2464-4G INJ10
C2464-5G INJ9
C0636-2G INJ1
C0636-8G INJ5
C0636-5G INJ3
C0636-9G INJ2
C0636-4G INJ4
C0636-3G INJ6
See Power Distribution
7. Check for codes P0201 - P0206 (injector faults)
and analyse these codes if present. Return to step
9 of this procedure if either P0171 or P0174 are
logged again after clearing the P0201 - P0206
codes.
8. Flow test the injectors:
Use a Rotunda Injector Tester or equivalent to
flow test the injectors according to the manufacturers instructions.
If any injector flow rate is not within specification,
replace the defective injector. Refit the injectors
and rerun the KOER Test.
If the injector flow rates are all within specification, the problem is not fuel related.
9. Check the cylinder compression pressures using
the service manual procedure.
If any compression pressure is low, repair the engine as necessary.
If the compression pressures are in specification,
carry out further analysis as for DTC P1131 to
check the heated oxygen sensors and circuits.