BRAKE warning message with no DTC's. CAN network faults/no comm concerns. Applies to Hyundai/KIA turbo charged vehicles equipped with vacuum pumps

Haris Technical Support Specialist New York Posted   Latest   Edited  
Tech Tip
2016 Hyundai Tucson Eco 1.6L (2) 7-spd (D7UF1)
Brake Light Illuminated
No Communication With Scan Tool

A quick tip on Hyundai/KIA turbo charged engines equipped with electric vacuum pumps. The vacuum pump is tied into the CAN network but is unable to generate DTC’s or display data. Water can potentially enter the pump due to the mounting location. The pump is attached to the transmission and sits relatively low. Water intrusion can potentially cause damage to the motor inside the pump. If the pump becomes inoperative or fails to generate enough vacuum, the BRAKE warning MIL illuminates. A CAN message is relayed from the pump to the cluster to illuminate BRAKE MIL, but no DTC’s set. Water intrusion can also short the CAN bus low, causing drivability/no start/NO COMM concerns.

BRAKE MIL: Verify brake fluid and park brake switches read off in the smart junction box data. Once verified start and run engine. Listen for pump operation using stethoscope/chassis ears while repeatedly depressing the brake pedal. If the pump does not turn on or makes an abnormal grinding/growling sound, replace the vacuum pump.

NO COMM: Measure voltage at CAN high/low at the DLC/MPCC. If readings are low (less than 1 volt each) unplug vacuum pump and recheck. If normal voltage resumes, replace the vacuum pump.

Simon Diagnostician
New Zealand
Simon Default

Many thanks Haris, great information

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Geoff Diagnostician
Geoff Default

Thank you. The "....tied into the CAN network but is unable to generate DTC’s or display data" is especially interesting! Wonder how many techs might think their scan tool is at fault in a situation like that.

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Danh Diagnostician
Viet Nam
Danh Default

Thank you very much. Exactly what Hyundai Tucson 2019 G 1.6 T-GDI (river fell) acted. Wish that I had read this sooner. I checked brake fluid, brake fluid switch, EPB motors, etc…finally I had to take it to Hyundai dealer and it's take them 2 days to found out what Mr​.​Kolenovic pointed out.

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