code 27

Discussion in 'Peterbilt Forum' started by Mr Dave, Jan 1, 2015.

  1. Mr Dave

    Mr Dave Light Load Member

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    Jan 2, 2011
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    07 pete 379 with c-15 acert motor. was low on coolant, but refilled. engine fan will not shut off and temp guage showing approx 200. shows a code 27. Is a sensor gone haywire? any help would be appreciated.
     
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  3. SAR

    SAR Road Train Member

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    Code 27 is coolant temp sensor open or short circuit. Your fan is staying on cause your ecm is seeing high coolant which is probably not or it is in safe mode. I would guess you have a damaged or chaffed wire leading to sensor or your sensor is haywire. On the main page of eighteen wheelers there is a docked thread showing fault codes and wiring schematics of engines. Good luck.
     
  4. SAR

    SAR Road Train Member

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    I should add my 3406E popped that code up one time. After letting truck warm up and start down the road the fan would all of a sudden come on around 155 degrees and soon after the check engine light on, then later the stop engine lamps comes on. Scared the bejeezus out of me. The code was 27 and I ended up replacing the sensor and solved it. It was a pita to get out and install new one.
     
  5. Mr Dave

    Mr Dave Light Load Member

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    Sensor gone haywire was what I thought. That sensor is located in a nipple coming out of the head near the t-stat housing?
     
  6. SAR

    SAR Road Train Member

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  7. Mr Dave

    Mr Dave Light Load Member

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    Thanks SAR for the info, had to take it to shop as sensor was buried under a/c bracket, a/c compressor. Good thing too , cuz 2 of the bolts on the a/c bracket broke and had to be drilled out. Took it to Brian's Diesel in El Reno, OK, good small shop, very reasonable rates and good people.
     
  8. SAR

    SAR Road Train Member

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    Not a problem. Glad you got it up and running again.
     
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