What does it mean?
C1734 is a Chassis (ABS, traction control, steering) fault code. It indicates: BCM (Control Unit) .
Symptoms
- Several unrelated warning lamps lit at the same time
- Functions handled by the module behaving intermittently: lighting, central locking, wipers, keyless entry
- Module dropping off the scan tool or refusing to communicate at all
- Code returning immediately after being cleared
- Battery going flat overnight because the vehicle will not go to sleep
Likely causes
- Low or unstable supply voltage from a weak battery, corroded battery terminals or a failing charging system
- Poor or corroded ground point for the control unit
- Water intrusion at the module connector or in the module location, causing green corrosion on the pins
- Configuration or software corrupted by a failed programming session, a flat battery or a jump start
- A shorted output load (for example a lamp or motor circuit) forcing the module driver to shut down
- Network fault making the module appear failed to the other controllers
- Genuine internal electronic failure of the control unit
How to fix it
- Test the battery and charging system first; nothing else can be judged with a weak supply
- Perform voltage drop tests on the module's power feeds and ground points
- Inspect the module connectors for water, green corrosion, pushed-out or spread terminals
- Read every module and address any network or lost communication codes before this one
- Disconnect suspect output circuits one at a time to find a shorted load pulling the module down
- Reflash the module to the latest calibration and reconfigure it if the software is suspect
- Replace and configure the control unit only after supply, ground, output circuits and network have all been proven good