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.
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HOMESERVICE MANUALSCHEVROLET2018SONIC LS, 1.8L ENG VIN H, AUTOMATIC TRANSREPAIR AND DIAGNOSIS (SINGLE PAGE)ACCESSORIES & EQUIPMENTHEADLIGHTSLIGHTING SYSTEMDIAGNOSTIC INFORMATION AND PROCEDURESSTOP LAMPS MALFUNCTIONCIRCUIT/SYSTEM TESTING
2018 Chevrolet Sonic LS, 1.8L Eng VIN H, Automatic Trans
Circuit/System Testing
2018 Chevrolet Sonic LS, 1.8L Eng VIN H, Automatic TransSECTION Circuit/System Testing
Brake Pedal Position Sensor Malfunction
- Ignition OFF, disconnect the harness connector at the B22 Brake Pedal Position Sensor, ignition ON.
- Test for less than 1 V between the appropriate low reference circuit terminal listed below and ground.
- Terminal 2 - with MM1
- Terminal A - with MM3
- If 1 V or greater
- Ignition OFF, disconnect the X1 harness connector at the K9 Body Control Module, ignition ON.
- Test for less than 1 V between the low reference circuit and ground.
- If 1 V or greater, repair the short to voltage on the circuit.
- If less than 1 V, replace the K9 Body Control Module.
- Go to next step: If less than 1 V
- Test or replace the B22 Brake Pedal Position Sensor.
Stop Lamps Malfunction
- Ignition OFF, exterior lamps OFF, trunk latch latched, remove the appropriate E5A Tail/Stop Lamp bulb.
- Test for less than 5 Ω between the ground circuit at the socket terminal and ground.
- If 5 Ω or greater
- Ignition OFF.
- Test for less than 2 Ω in the ground circuit end to end.
- If 2 Ω or greater, repair the open/high resistance in the circuit.
- If less than 2 Ω, repair the open/high resistance in the ground connection.
- Go to next step: If less than 5 Ω
- Connect a test lamp between the control circuit at the socket terminal and ground, ignition ON.
- Verify the test lamp turns ON and OFF when commanding the appropriate Rear Brake/Park Lamp ON and OFF with a scan tool.
- If the test lamp is always OFF
- Ignition OFF, disconnect the appropriate harness connector listed below at the K9 Body Control Module.
- X4 left stop lamp
- X5 right stop lamp
- Test for infinite resistance between the control circuit and ground.
- If less than infinite resistance, repair the short to ground on the circuit.
- Go to next step: If infinite resistance
- Test for less than 2 Ω in the control circuit end to end.
- If 2 Ω or greater, repair the open/high resistance in the circuit.
- If less than 2 Ω, replace the K9 Body Control Module.
- If the test lamp is always ON
- Ignition OFF, disconnect the appropriate harness connector listed below at the K9 Body Control Module, ignition ON.
- X4 left stop lamp
- X5 right stop lamp
- Test for less than 1 V between the control circuit terminal and ground.
- If 1 V or greater, repair the short to voltage on the circuit.
- If less than 1 V, replace the K9 Body Control Module.
- Go to next step: If the test lamp turns ON and OFF
- Test or replace the appropriate E5A Tail/Stop Lamp.
Center High Mount Stop Lamp Malfunction
- Ignition OFF, exterior lamps OFF, trunk latch latched, disconnect the harness connector at the E6 Center High Mounted Stop Lamp.
- Test for less than 5 Ω between the appropriate ground circuit terminal listed below and ground.
- Terminal B - with TS6
- Terminal 2 - with D59
- If 5 Ω or greater
- Ignition OFF.
- Test for less than 2 Ω in the ground circuit end to end.
- If 2 Ω or greater, repair the open/high resistance in the circuit.
- If less than 2 Ω, repair the open/high resistance in the ground connection.
- Go to next step: If less than 5 Ω
- Connect a test lamp between the appropriate control circuit terminal listed below and ground, ignition ON.
- Terminal A - with TS6
- Terminal 1 - with D59
- Verify the test lamp turns ON and OFF when commanding the Center Brake Lamp ON and OFF with a scan tool.
- If the test lamp is always OFF
- Ignition OFF, disconnect the X4 harness connector at the K9 Body Control Module.
- Test for infinite resistance between the control circuit and ground.
- If less than infinite resistance, repair the short to ground on the circuit.
- Go to next step: If infinite resistance
- Test for less than 2 Ω in the control circuit end to end.
- If 2 Ω or greater, repair the open/high resistance in the circuit.
- If less than 2 Ω, replace the K9 Body Control Module.
- If the test lamp is always ON
- Ignition OFF, disconnect the X4 harness connector at the K9 Body Control Module, ignition ON.
- Test for less than 1 V between the control circuit terminal and ground.
- If 1 V or greater, repair the short to voltage on the circuit.
- If less than 1 V, replace the K9 Body Control Module.
- Go to next step: If the test lamp turns ON and OFF
- Test or replace the E6 Center High Mounted Stop Lamp.
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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.