Aston Martin diagnostic trouble code
P1935: Invalid Brake Signal
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
- DB9
- Warning-lamp status
- DB9: Non-MIL
What Aston Martin code P1935 means
Invalid Brake Signal
DB9 preliminary diagnostic manual · section 2-290
Manufacturer fault-analysis procedure
Manual fault definition
P1935 - Invalid brake signal.
Cautions and notes
CAUTION: This code may be generated only in
the Primary Powertrain Control Module (PCM).
Check that you are working on the correct half of
the engine.
the Primary Powertrain Control Module (PCM).
Check that you are working on the correct half of
the engine.
Test sequence and decision path
1. Connect the WDS and confirm that a P1935 code
is logged . Clear the P1935 code.
2. Install the breakout box to the PCM in which the
P1935 was logged.
3. Brake Pedal Switch (BPS) - Monitor the Brake
Pedal Switch signal at either C0635-7 (primary) or
C0638-7 (secondary). Press the brake pedal. The
BPS signal should switch from 12 to 0 volts when
the pedal is pressed and return to 12 volts when
the brake pedal is released.
If the signal switches correctly from 12 - 0 - 12
volts when the brake pedal is pressed and
released, the fault is not present at this time.
Check the connectors for intermittent
connections, loose pins, etc. Service the circuit as
necessary. Repeat the voltage check to ensure
that the problem is resolved.
If the BPS signal does not switch to 0 volts when
the brake pedal is pressed, go to step 4.
4. Ignition off. Complete a continuity check from
PCM pin C0635-7 (or C0638-7), through the
brake switch to Central Electronic Module pin
C0586-28. Press and release the brake pedal.
Continuity should be broken when the brake
pedal is pressed.
If continuity is good but the signal does not go
open circuit when the brake pedal is pressed,
service/adjust the brake switch as necessary.
Clear the P1935 code and retest the circuit to
ensure that the problem is resolved.
Open the corresponding manual page for wiring diagrams and figures
is logged . Clear the P1935 code.
2. Install the breakout box to the PCM in which the
P1935 was logged.
3. Brake Pedal Switch (BPS) - Monitor the Brake
Pedal Switch signal at either C0635-7 (primary) or
C0638-7 (secondary). Press the brake pedal. The
BPS signal should switch from 12 to 0 volts when
the pedal is pressed and return to 12 volts when
the brake pedal is released.
If the signal switches correctly from 12 - 0 - 12
volts when the brake pedal is pressed and
released, the fault is not present at this time.
Check the connectors for intermittent
connections, loose pins, etc. Service the circuit as
necessary. Repeat the voltage check to ensure
that the problem is resolved.
If the BPS signal does not switch to 0 volts when
the brake pedal is pressed, go to step 4.
4. Ignition off. Complete a continuity check from
PCM pin C0635-7 (or C0638-7), through the
brake switch to Central Electronic Module pin
C0586-28. Press and release the brake pedal.
Continuity should be broken when the brake
pedal is pressed.
If continuity is good but the signal does not go
open circuit when the brake pedal is pressed,
service/adjust the brake switch as necessary.
Clear the P1935 code and retest the circuit to
ensure that the problem is resolved.