CAN Bus Communication Failure U1900
The U1900 code indicates that the Powertrain Control Module (PCM) or another control module has detected a failure in the Controller Area Network (CAN) bus communication. Specifically, the module cannot transmit or receive messages on the high-speed (HS-CAN) or medium-speed (MS-CAN) bus within the expected time, suggesting a data bus fault, a defective module saturating the bus, or a wiring/grounding issue.
1. Commonly Affected Makes
2. Most Common Causes
- CAN bus wiring open, shorted to ground, shorted to battery, or shorted between CAN+ and CAN- lines
- Damaged, corroded, or loose terminals in connectors at the DLC or control modules
- Faulty control module (PCM, ABS, IPC, BCM, etc.) blocking communication
- Low battery voltage or charging system failure affecting module logic
- Aftermarket accessories (alarm, radio, GPS tracker) improperly installed and interfering with the bus
- Missing or damaged CAN bus termination resistors
3. Symptoms You Will Notice
- Check Engine Light or other warning lights illuminated
- Multiple systems inoperative or erratic behavior (e.g., transmission, ABS, instrument cluster)
4. Step-by-Step Diagnosis
Scan all modules for communication faults and document codes
Check battery voltage and charging system; ensure at least 12.6V
Inspect CAN bus wiring for damage, corrosion, or shorts using a multimeter
Measure resistance between CAN High and CAN Low at the DLC; should be approximately 60 ohms
Disconnect aftermarket accessories to test for interference
Isolate the faulty module by disconnecting modules one at a time while monitoring bus activity
5. Frequently Asked Questions
Is it safe to drive?▼
No, driving with a U1900 code is not recommended as it can cause unpredictable behavior in critical systems like transmission and brakes, posing a safety risk.
How much does it cost to fix?▼
Repair costs vary widely: from $100 for a simple wiring repair to $1,000+ for module replacement, plus diagnostic fees.