P1609

What it means

On Cadillac, P1609 means the engine control module has lost the serial data signal from the traction control system (TCS). The ECM expects regular messages from the traction control or brake control module and set the code when they stopped arriving or were not valid. The exact network and module layout depends on the model and year.

Symptoms

• Traction control warning light on
• Check engine light on
• Traction control or stability control inactive
• ABS light on at the same time on some models
• Possible reduced engine power or torque intervention on some models
• Intermittent fault that comes and goes with bumps or damp weather

Possible causes

• Wiring or connector fault in the serial data circuit between the ECM and the traction control or brake control module (chafed, corroded, loose or open circuit)likely
• Low battery voltage or poor power and earth supply to the traction control or brake modulelikely
• Blown fuse or faulty relay feeding the traction control or brake control modulepossible
• Faulty traction control or brake control module that is not transmittingpossible
• Other network faults on the vehicle data bus pulling the signal down, such as another module with a shortpossible
• Fault inside the ECM, or outdated software where the manufacturer has issued a correction for this modelrare

How to diagnose

1. Read all stored and pending codes from every module, noting any ABS, traction control or network communication codes, and record the freeze frame data.
2. Check battery condition and charging voltage, as low voltage commonly causes communication codes.
3. Check the fuses and relays supplying the ECM and the traction control or brake module against the wiring diagram for the model.
4. Inspect the wiring, connectors and earth points between the ECM and the brake or traction control module for damage, water ingress, corrosion or poor pin tension.
5. Check the module power and earth supplies with a multimeter, including voltage drop under load.
6. Test the serial data circuit for continuity, short to earth and short to voltage using the wiring diagram, and check the signal with a scope if available.
7. Check the traction control module communicates with the scan tool; if not, suspect that module or its supply.
8. Check for manufacturer software updates or service bulletins for the model and, only after wiring and supplies are proven good, consider module faults.

How to fix

• Repair or replace damaged wiring and clean or replace corroded connectors on the serial data circuit.
• Restore proper power and earth connections, and charge or replace a weak battery.
• Replace the blown fuse or faulty relay after finding why it failed.
• Replace or repair the faulty traction control or brake control module, then programme or set it up as the model requires.
• Update the ECM or module software where an outdated calibration is a known cause for that model.

Can I keep driving?

This code for other makes

• P1609BMWSerial Communicating Link EML
• P1609BuickLoss Of TCS Serial Data
• P1609ChevroletLoss Of TCS Serial Data
• P1609GMLoss Of TCS Serial Data
• P1609GMCLoss Of TCS Serial Data
• P1609JaguarInternal Control Module CPU To CPU Communication Failure
• P1609MazdaPowertrain Control Module ECM CPU Knock Sensor Circuit
• P1609OldsmobileLoss Of TCS Serial Data
• P1609OtherDiagnostic Lamp Driver Fault
• P1609SaturnLoss Of TCS Serial Data
• P1609VolkswagenCrash Shut Down Activated

Nearby codes

• P1608CadillacSerial Communication Problem With Device 8
• P1610CadillacLoss Of PZM Serial Data