MG 4 Gear Selector: Difference between revisions
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!CanId | !CanId | ||
!Message | !Message | ||
!Direction | |||
!0 | !0 | ||
!1 | !1 | ||
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|0x09D | |0x09D | ||
|Shifter Status (from Shifter) | |Shifter Status (from Shifter) | ||
|From Shifter | |||
|CRC8 (bytes1-7) | |CRC8 (bytes1-7) | ||
|Counter 4-bit | |Counter 4-bit | ||
| Line 95: | Line 97: | ||
|- | |- | ||
|0x047 | |0x047 | ||
|Msg1 | |Control Msg1 | ||
"Activate Shifter"? | "Activate Shifter"? | ||
|To Shifter | |||
|CRC8 (bytes1-7) | |CRC8 (bytes1-7) | ||
|Counter 4-bit | |Counter 4-bit | ||
| Line 108: | Line 111: | ||
|- | |- | ||
|0x12a | |0x12a | ||
|Msg2 | |Control Msg2 | ||
|To Shifter | |||
|CRC8 (bytes1-7) | |CRC8 (bytes1-7) | ||
|Counter 4-bit | |Counter 4-bit | ||
| Line 120: | Line 124: | ||
|- | |- | ||
|0x2b6 | |0x2b6 | ||
|Msg3 | |Control Msg3 | ||
|To Shifter | |||
|00 | |00 | ||
|00 | |00 | ||
Revision as of 18:44, 15 August 2025
General Information
MG 4 uses a rotary gear selector.
Neutral corresponds to the central rest postion, Reverse is selected by an anticlockwise twist, Drive by clockwise rotation of the gear knob.
Park is selected by pressing the gear knob.
Selected gear is communicated by CAN.
The unit incorporates three LEDs across the top of the unit which correspond to Reverse, Neutral and Drive.
The knob itself lights up in Yellow when Park is selected.
Part Numbers
SAIC Motor Shift-by-wire : 11357121
Pinout and Connector
The shifter uses a 12 way connector, of which only 5 pins are connected.
Required plug is:
Molex 347290122 : https://www.molex.com/en-us/products/part-detail/0347290122
When viewed from the rear of the unit, Pin1 is top-left, Pin12 is bottom right.
| Pin | OEM Wire Colour | Function |
|---|---|---|
| 1 | Black/Yellow | 12V |
| 5 | Pink/White | 12V WakeupEnable |
| 7 | Yellow/Blue | PT-CAN Ext High |
| 8 | Green/Yellow | PT-CAN Ext Low |
| 12 | Black | GND |
Operation
On poweron, the selector will start in the PARK position, and this will be communicated in message 0x09D
To enable shifting three messages must be sent to the shifter, repeated at 50ms, CanIds: 0x047, 0x12a, 0x2b6 as described below.
Stopping sending the 0x47 message will cause the shifter to enter into PARK position and prevent a gear being selected.
Restarting 0x47 messages will re-enable the shifter and allow a gear to be selecte.
CAN Bus
The Powertrain CAN Bus has a baud rate of 500kBaud.
Most messages have a standard CRC-8-SAE J1850. (polynomial 0x1D)
CAN Messages are sent every 50ms.
Observed data is described below.
| CanId | Message | Direction | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
|---|---|---|---|---|---|---|---|---|---|---|
| 0x09D | Shifter Status (from Shifter) | From Shifter | CRC8 (bytes1-7) | Counter 4-bit
F0-FF |
03 | POS1 | POS2 | F0|F1 | 38|39 | FF |
| 0x047 | Control Msg1
"Activate Shifter"? |
To Shifter | CRC8 (bytes1-7) | Counter 4-bit
00-0F |
45 | 9B | 7F | FF | FF | FE|FF |
| 0x12a | Control Msg2 | To Shifter | CRC8 (bytes1-7) | Counter 4-bit
F0-FF |
FF | FF | FF | FF | FF | 01|11|13|14 |
| 0x2b6 | Control Msg3 | To Shifter | 00 | 00 | 02 | 00 | 00 | 00 | 00 | 00 |
The Gear selection is communicated over CAN, and can be decoded as follows.
POS1 is sufficent to indicate the selected gear.
| Selected Gear | POS1 | POS2 | |
|---|---|---|---|
| DRIVE | 05 | 0A | |
| NEUTRAL | 06 | 09 | |
| REVERSE | 07 | 08 | |
| PARK | 08 | 07 |