Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Diagnosis System
- DESCRIPTION
- DIAGNOSTIC SYSTEM
When troubleshooting a vehicle with a diagnostic system, the only difference from the usual troubleshooting procedure is connecting the hand-held tester to the vehicle and reading various data output from the vehicle's transmission control ECU assy.
The transmission control ECU assy records DTCs when the computer detects a malfunction in the computer itself or in its circuits.
To check the DTCs, connect the hand-held tester to the DLC3 on the vehicle. The hand-held tester enables you to erase the DTCs, activate the several actuators and check freeze frame data and data list.
- Check the DLC3.
The transmission control ECU assy follows the CAN and ISO 9141-2 communication protocol. The terminal arrangement of the DLC3 complies with SAE J1962 and matches the ISO 9141-2 format.
- DIAGNOSTIC SYSTEM
| Symbols (Terminals No.) | Terminal Description | Condition | Specified Condition |
|---|---|---|---|
| SIL(7) - SG(5) | Bus "+" line | During communication | Pulse generation |
| CG(4) - Bodyground | Chassis ground | Always | Below 1Ω |
| SG(5) - Bodyground | Signal ground | Always | Below 1Ω |
| BAT(16) - Bodyground | Battery positive | Always | 11 to 14V |
| CANH(6) -CANL(14) | HIGH-level CAN bus line | Power switch off | 54 to 67 Ω |
| CANH(6) - Battery positive | HIGH-level CAN bus line | Power switch off | 1 MΩ or higher |
| CANH(6) - CG(4) | HIGH-level CAN bus line | Power switch off | 3 KΩ or higher |
| CANL(14) - Battery positive | LOW-level CAN bus line | Power switch off | 1 MΩ or higher |
| CANL(14) - CG(4) | LOW-level CAN bus line | Power switch off | 3 KΩ or higher |
HINT:
If the display shows "UNABLE TO CONNECT TO VEHICLE" after connecting the hand-held tester cable to the DLC3 and turning the power switch on (IG), there is a problem with either the vehicle or tester.
- If communication is normal when connecting the tester to another vehicle, inspect the DLC3 on the original vehicle.
- If communication is still not possible when connecting the tester to another vehicle, the problem is probably on the tester itself, so consult the Service Department listed in the tester's operator's manual.
NO RELATED
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.