General Assist Technical Reference
Forward and Reverse Signal Error Codes
Understanding three-digit communication error codes on G model and VRF systems
Applies to: G model and VRF systems that display three-digit error codes in the controller error history.
How the error code is interpreted
Some G model and VRF controllers display an error code using three digits. The third digit provides additional detail about the fault and can be used to identify whether a communication fault is a forward or reverse transmission error, and whether it occurred at start-up or during operation.
Important: Do not treat all 11.x communication faults as the same fault. The third digit changes the detailed classification and should be recorded exactly as displayed.
Communication error detail classification
| Error code | Detail classification |
|---|---|
| 11.1 | Serial reverse transmission error at start-up |
| 11.2 | Serial reverse transmission error during operation |
| 11.3 | Serial forward transmission error at start-up |
| 11.4 | Serial forward transmission error during operation |
Quick reference
| Third digit | Transmission direction | When detected |
|---|---|---|
| 1 | Reverse | At start-up |
| 2 | Reverse | During operation |
| 3 | Forward | At start-up |
| 4 | Forward | During operation |
Service use
- Open the controller error history and record the complete three-digit code.
- Use the third digit to identify the detailed communication fault classification.
- Confirm whether the fault occurred at start-up or while the system was operating.
- Use the applicable service manual troubleshooting procedure for the exact code displayed.
Note: This reference explains the detailed classification of the 11.1 to 11.4 communication error codes only. It does not provide the diagnostic procedure or identify the component responsible for the communication failure.