What does it mean?
U1016 is a Network (CAN bus, module communications) fault code. It indicates: No Communication With Powertrain Control Module .
Symptoms
- Engine cranks but will not start, or does not crank at all
- Check engine light (MIL) and several other warning lamps on together
- Scan tool cannot connect to the engine controller although other modules respond
- Speedometer, tachometer and other engine-driven gauges dead or erratic
- Immobiliser or security message on the display
- Multiple communication codes stored in every module that expects PCM data
Likely causes
- PCM has no power or ground because of a blown fuse, failed relay or corroded ground point
- Open circuit in the bus wiring between the PCM and the rest of the network
- Both bus lines shorted together, or one line shorted to ground or to battery voltage
- Corroded or disconnected PCM connector, or a connector damaged during previous work
- Internal PCM failure, including a dead processor or transceiver stage
- Terminating resistor failure at the end of the bus segment
- A different module dragging the bus down and blocking all traffic
How to fix it
- Try to connect to the PCM with a scan tool; if no module at all responds, suspect the diagnostic connector power or ground first
- Check every fuse and relay that feeds the PCM, including the main and ignition supplies
- Measure PCM power feeds and grounds with the ignition on and do a voltage drop test on the ground circuits
- Measure the resistance across the two bus lines at the diagnostic connector with the ignition off and compare with the expected terminated value
- Check each bus line for a short to ground and a short to battery voltage
- Disconnect modules one at a time to find a module that is pulling the bus down and restoring communication when unplugged
- Inspect the PCM connectors for corrosion, water and pushed-back pins, then reseat them
- Consider PCM replacement and programming only after supply, ground and bus integrity have all been proven