SYS.OK|MANUAL.DB● LIVE
HOMESERVICE MANUALSCHEVROLET2025TRAILBLAZER RS, 4WDREPAIR AND DIAGNOSIS (SINGLE PAGE)ACCESSORIES & EQUIPMENTCOMMUNICATION DEVICESDATA COMMUNICATIONS - DIAGNOSTIC INFORMATION AND PROCEDURES (2 OF 2)DIAGNOSTIC INFORMATION AND PROCEDURESSCAN TOOL DOES NOT COMMUNICATE WITH GATEWAY ISOLATED LOW SPEED GMLAN DEVICECIRCUIT/SYSTEM VERIFICATION
2025 Chevrolet Trailblazer RS, 4WD

Circuit/System Verification

2025 Chevrolet Trailblazer RS, 4WDSECTION Circuit/System Verification
  1. Ignition ON/Vehicle In Service Mode.
  2. Verify that the scan tool is communicating with vehicle.
    • Go to next step: If the scan tool is communicating with vehicle 
  3. Verify that DTC U0073, U0074, U0075, U0076 U0077, U0078, U007A, P06E4, P1EB9, U1814, U2099, B1325, B1330, B1370, B1380, B1424, B1428, B1440, B1441, B1517, C0800, C0899, C12E1, P0560, or P0562 is not set.
    • Go to next step: If none of the DTCs are set 
  4. Attempt to communicate with all devices on the gateway isolated low speed GMLAN bus. Refer to Data Link References  to determine which devices are on the gateway isolated low speed GMLAN bus.
  5. Verify two or more devices are not communicating on the gateway isolated low speed GMLAN bus.
    • If only one device is not communicating 

      Refer to Circuit/System Testing - Testing the Device Circuits.

    • Go to next step: If two or more devices are not communicating 
  6. Ignition/Vehicle OFF, disconnect the scan tool from the X84 Data Link Connector. The following tests will be done at the X84 Data Link Connector.
  7. Ignition ON/Vehicle In Service Mode.
  8. Test for less than 4.5 V between the serial data circuit terminal 1 and ground.
    • If 4.5 V or greater 

      Repair the short to voltage in the serial data circuit between the X84 Data Link Connector and the K56 Serial Data Gateway Module.

    • Go to next step: If less than 4.5 V 
  9. Ignition/Vehicle OFF, all access doors closed, all vehicle systems OFF, and all keys at least 3 m (9.8 ft) away from vehicle. It may take up to 10 min for all vehicle systems to power down.
  10. Test for greater than 100 Ω between the serial data circuit terminal 1 and ground.
    • If 100 Ω or less 

      Repair the short to ground in the serial data circuit between the X84 Data Link Connector and the K56 Serial Data Gateway Module.

    • Go to next step: If greater than 100 Ω 
  11. Test for less than infinite resistance between the serial data circuit terminal 1 and ground.
    • If infinite resistance 

      Repair the open/high resistance in the serial data circuit between the X84 Data Link Connector and the K56 Serial Data Gateway Module.

    • Go to next step: If less than infinite resistance 
  12. Refer to Circuit/System Testing - Serial Data Starting Point.
RENDER: 1.0x

NO RELATED

Recommended Tools & Savings

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.

Shop Manual-Ready ToolsFree Quote CheckQuote Shield Pro

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.