Aston Martin diagnostic trouble code
P1789: Low Battery Voltage with Turbine Speed (7V-9V)
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 P1789 means
Low Battery Voltage with Turbine Speed (7V-9V)
DB9 preliminary diagnostic manual · section 2-274
Manufacturer fault-analysis procedure
Manual fault definition
P1789 - Low Battery Voltage Input to the TCM
Test sequence and decision path
1. Key off. Access the transmission harness and disconnect the transmission connector.
2. Check the voltage from harness connector
C0932-14 to C0932-13 and 16.
If +12 volts is measured, go to step 3.
If the +12 volt supply is below specification,
check the battery charging and +12 volt circuit
integrity to C0932-14. Service the charging system or wiring as necessary. Reconnect all components and run a brief road test to ensure that the
problem is resolved.
3. Check the condition of the transmission connector socket pin C0932-14.
If the socket is damaged, service the wiring as
necessary. reconnect all components and run a
brief road test to ensure that the problem is
resolved.
If the socket is serviceable, go to step 4.
4. Reconnect the harness. Using WDS, monitor
VBATT during a road test. Also connect a voltmeter between boot fusebox F12 and ground. Run a
road test.
If VBATT is stable on the WDS and on the meter,
the prnblem is not present at this time and testing
is complete.
If VBATT is steady on the meter but unstable on
WDS, perform a continuity check from F12 to
C0932-=14. If continuity is good, change the
mechatronic unit and run a further road test to
ensure that the problem is resolved.
5. If a continuity problem is identified, service the
wiring as necessary. Run a further road test to
ensure that the problem is resolved.
Open the corresponding manual page for wiring diagrams and figures
2. Check the voltage from harness connector
C0932-14 to C0932-13 and 16.
If +12 volts is measured, go to step 3.
If the +12 volt supply is below specification,
check the battery charging and +12 volt circuit
integrity to C0932-14. Service the charging system or wiring as necessary. Reconnect all components and run a brief road test to ensure that the
problem is resolved.
3. Check the condition of the transmission connector socket pin C0932-14.
If the socket is damaged, service the wiring as
necessary. reconnect all components and run a
brief road test to ensure that the problem is
resolved.
If the socket is serviceable, go to step 4.
4. Reconnect the harness. Using WDS, monitor
VBATT during a road test. Also connect a voltmeter between boot fusebox F12 and ground. Run a
road test.
If VBATT is stable on the WDS and on the meter,
the prnblem is not present at this time and testing
is complete.
If VBATT is steady on the meter but unstable on
WDS, perform a continuity check from F12 to
C0932-=14. If continuity is good, change the
mechatronic unit and run a further road test to
ensure that the problem is resolved.
5. If a continuity problem is identified, service the
wiring as necessary. Run a further road test to
ensure that the problem is resolved.