Aston Martin diagnostic trouble code
P0721: Output Shaft Speed Sensor Circuit Range/Performance
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
- Electrical and control modules
- Manual coverage
- DB9
- Warning-lamp status
- DB9: MIL
What Aston Martin code P0721 means
Output Shaft Speed Sensor Circuit Range/Performance
DB9 preliminary diagnostic manual · section 2-170
Manufacturer fault-analysis procedure
Cautions and notes
NOTE: Vehicle speed is sensed from the diff speed sensor on auto cars and from the gearbox output speed
sensor on manual cars.
sensor on manual cars.
Test sequence and decision path
1. Connect the WDS and confirm that P0720,
P0721 or P0722 is logged. Clear the logged fault
code.
2. Set datalogger to monitor the VSS signal. run a
brief road test (or rolling road test) with varying
speeds.
Check if the recorded vehicle speed matches the
actual speed.
If the recorded speed does not match actual
speed, go to step 3 for manual cars or step 4 for
automatic cars.
If the VSS readings are accurate and no relevant
fault codes are logged, retest at low speeds and
check the lowest speed which can be monitored.
For low speed errors, check the following:
Sensor air gap
Sensor damage
If no errors are detected, treat this as an intermittent problem and service the VSS circuit for poor
connections and shorts to power or ground
Run an extended road test to ensure that the
problem is resolved.
3. For Manual Cars:
Perform continuity checks between the following
connections:
VSS+ C1561-2 to primary PCM C0635-32 and
secondary PCM C0638-32.
VSS- C1561-1 to primary PCM C0635-33 and
secondary PCM C0638-33.
If any circuit fault is detected, service the circuit
as necessary. Clear the fault code and run a brief
road or rolling road test to ensure that the problem is resolved.
4. For Auto Cars:
Perform continuity checks between the following
connections:
VSS+ C0195-2 to primary PCM C0635-32 and
secondary PCM C0638-32.
VSS- C0195-1 to primary PCM C0635-33 and
secondary PCM C0638-33.
If any circuit fault is detected, service the circuit
as necessary. Clear the fault code and run a brief
road or rolling road test to ensure that the problem is resolved.
Open the corresponding manual page for wiring diagrams and figures
P0721 or P0722 is logged. Clear the logged fault
code.
2. Set datalogger to monitor the VSS signal. run a
brief road test (or rolling road test) with varying
speeds.
Check if the recorded vehicle speed matches the
actual speed.
If the recorded speed does not match actual
speed, go to step 3 for manual cars or step 4 for
automatic cars.
If the VSS readings are accurate and no relevant
fault codes are logged, retest at low speeds and
check the lowest speed which can be monitored.
For low speed errors, check the following:
Sensor air gap
Sensor damage
If no errors are detected, treat this as an intermittent problem and service the VSS circuit for poor
connections and shorts to power or ground
Run an extended road test to ensure that the
problem is resolved.
3. For Manual Cars:
Perform continuity checks between the following
connections:
VSS+ C1561-2 to primary PCM C0635-32 and
secondary PCM C0638-32.
VSS- C1561-1 to primary PCM C0635-33 and
secondary PCM C0638-33.
If any circuit fault is detected, service the circuit
as necessary. Clear the fault code and run a brief
road or rolling road test to ensure that the problem is resolved.
4. For Auto Cars:
Perform continuity checks between the following
connections:
VSS+ C0195-2 to primary PCM C0635-32 and
secondary PCM C0638-32.
VSS- C0195-1 to primary PCM C0635-33 and
secondary PCM C0638-33.
If any circuit fault is detected, service the circuit
as necessary. Clear the fault code and run a brief
road or rolling road test to ensure that the problem is resolved.