Aston Martin diagnostic trouble code
P0634: PCM / ECM / TCM Internal Temperature Too High Or Sensor Failure
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
- Transmission
- Manual coverage
- DB9
- Warning-lamp status
- DB9: MIL
What Aston Martin code P0634 means
PCM / ECM / TCM Internal Temperature Too High Or Sensor Failure
DB9 preliminary diagnostic manual · section 2-152
Manufacturer fault-analysis procedure
Test sequence and decision path
1. Connect the WDS or scan tool. Confirm that
P0634 is logged.
2. Using the Service Manual procedure, check and
if necessary top up the automatic gearbox fluid.
If the transmission fluid level is correct, go to step
3. If it was necessary to add a significant amount of
transmission fluid, there is a strong possibility that
low transmission fluid was the cause of the overheat condition. Clear the P0634 code and run a
brief road test to ensure that the fault condition is
cleared.
3. Check for any reports of poor shift quality.
If shift is poor, check the cleanliness of the transmission fluid etc. Check filler plug for dirt?
4. Examine the transmission fluid cooling circuit for
damage or restrictions which could inhibit the
fluid cooling function.
If no fault symptom is found, go to step 4.
If any fault is identified, service the cooling circuit
as necessary. Top up the transmission fluid. Clear
the P0634 code and run a brief road test to
ensure that the problem is resolved.
5. Check that the owner has not been driving the car
in a particularly fast or competitive style or in
very hot weather which could have caused the
overheat.
If the car has been driven conservatively and
weather conditions are not the cause of the overheat, go to step 6.
If the car has been driven hard, advise the owner
to avoid “Transmission Overtemperature’ conditions.
6. Set the datalogger to monitor engine coolant temperature and transmission temperature. Road test
the car for about 15-20 miles including as many
gearshifts as can be safely included.
Stop the test and note the engine coolant temperature and transmission fluid temperature.
The transmission should always be significantly
cooler than the engine.
If possible, check the transmission temperature
with an external thermometer to cross check the
temperature sensor indication.****
7. Key off. Disconnect the transmission harness at
the gearbox.
8. With the ignition switched off, check for +12 vots
from transmission harness connector pin C 0932-
14 (VBatt) to pin C0932-13 and 16 (Ground)
If +12 volts is available, go to step 7.
If +12 volts is not available, service the +12 volt
or ground circuit as necessary. Clear the fault
code and run a KOER test to ensure that the problem is resolved.
9. Key on. Check for +12 volts from C0932-9 (+12
Ign) to C0932-13.
If +12v is available, go to step 5.
If +12v is not available, service the +12V Ignition
line to C0932-9. Clear the fault code and run a
KOER test to ensure that the problem is resolved.
10. The temperature sensor is integrated into the
‘Mechatronic Unit” in the gearbox and is not
serviceable. Change the mechatronic unit. Clear
the fault code and run a KOER test to ensure that
the problem is resolved.
11. Check for muck in the transmission fluid. i.e.
blockages in the cooling system
Open the corresponding manual page for wiring diagrams and figures
P0634 is logged.
2. Using the Service Manual procedure, check and
if necessary top up the automatic gearbox fluid.
If the transmission fluid level is correct, go to step
3. If it was necessary to add a significant amount of
transmission fluid, there is a strong possibility that
low transmission fluid was the cause of the overheat condition. Clear the P0634 code and run a
brief road test to ensure that the fault condition is
cleared.
3. Check for any reports of poor shift quality.
If shift is poor, check the cleanliness of the transmission fluid etc. Check filler plug for dirt?
4. Examine the transmission fluid cooling circuit for
damage or restrictions which could inhibit the
fluid cooling function.
If no fault symptom is found, go to step 4.
If any fault is identified, service the cooling circuit
as necessary. Top up the transmission fluid. Clear
the P0634 code and run a brief road test to
ensure that the problem is resolved.
5. Check that the owner has not been driving the car
in a particularly fast or competitive style or in
very hot weather which could have caused the
overheat.
If the car has been driven conservatively and
weather conditions are not the cause of the overheat, go to step 6.
If the car has been driven hard, advise the owner
to avoid “Transmission Overtemperature’ conditions.
6. Set the datalogger to monitor engine coolant temperature and transmission temperature. Road test
the car for about 15-20 miles including as many
gearshifts as can be safely included.
Stop the test and note the engine coolant temperature and transmission fluid temperature.
The transmission should always be significantly
cooler than the engine.
If possible, check the transmission temperature
with an external thermometer to cross check the
temperature sensor indication.****
7. Key off. Disconnect the transmission harness at
the gearbox.
8. With the ignition switched off, check for +12 vots
from transmission harness connector pin C 0932-
14 (VBatt) to pin C0932-13 and 16 (Ground)
If +12 volts is available, go to step 7.
If +12 volts is not available, service the +12 volt
or ground circuit as necessary. Clear the fault
code and run a KOER test to ensure that the problem is resolved.
9. Key on. Check for +12 volts from C0932-9 (+12
Ign) to C0932-13.
If +12v is available, go to step 5.
If +12v is not available, service the +12V Ignition
line to C0932-9. Clear the fault code and run a
KOER test to ensure that the problem is resolved.
10. The temperature sensor is integrated into the
‘Mechatronic Unit” in the gearbox and is not
serviceable. Change the mechatronic unit. Clear
the fault code and run a KOER test to ensure that
the problem is resolved.
11. Check for muck in the transmission fluid. i.e.
blockages in the cooling system