What does it mean?
U1199 is a Network (CAN bus, module communications) fault code. It indicates: Lost Hood Ajar Switch Voltage Message .
Symptoms
- Alarm triggers by itself or the system refuses to arm
- Hood-open warning stays on the cluster with the hood shut, or never appears when it is open
- Under-hood or courtesy lamp stays lit and drains the battery
- Remote arming functions of the key fob do not respond
- Scan tool loses communication with the body modules now and then
- Other network codes stored alongside this one
Likely causes
- Hood ajar switch stuck open or closed by corrosion, a bent bracket or a misaligned plunger
- Open, chafed or shorted wiring between the hood switch and the module that reports its state
- Corroded or backed-out terminals in the body harness connector at the switch or at the module
- The transmitting module drops off the SCP bus because of an open bus wire, a bad splice or a damaged section of harness
- Poor power feed or ground at the transmitting module, so it stops broadcasting intermittently
- Water intrusion into the connector where the harness passes into the engine compartment
- Internal failure or wrong calibration in the module that broadcasts hood status
How to fix it
- Scan every module, record freeze frame data, then clear the codes and see which ones come back
- Watch the live hood ajar status while operating the switch by hand
- Inspect the switch, its bracket and its alignment; look for rust and water inside the plunger
- Test the switch signal wire for open circuit, short to ground and short to battery with a multimeter
- Inspect the SCP bus wiring and the module connectors for green corrosion, spread terminals and wet pins
- Verify module power and ground with a voltage drop test under load
- Replace the hood switch if it fails testing; reprogram or replace the module only after the wiring is proven good