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BMW E704 IHKA : K-CAN Line fault

Fault code E704 IHKA : K-CAN line fault is related to the CAN line problem. fault code always come with E72D no message ( control valve in the air conditioning compressor, 0x2DE) receive integrated automatic heating/air conditioning system, transmitter JBE, E71E no message ( torque 0x0AA), receive IHKA, transmitter DME-DDE. When Junction box electronic control module (JBE) detect wrong or No signal from rear HVAC controller then fault code E704 IHKA : K-CAN line fault. It is quit possible that when this fault code is store in JBE the air conditioning system may become inoperative.

BMW use two wire K-CAN line system to connect several control module like climate control module (IHKA), airbag control module, ride height control module (EHC), tire pressure control module (TPMS), junction box electronic (JBE), instrument cluster meter etc. this two wire K-CAN line make communication with all these control module. Failure of K-CAN line can cause the fault code to be store in every control module.

Damage K-CAN Line

Causes of E704 IHKA : K-CAN line fault :

  • Faulty or damage can wiring harness of K-CAN line.
  • A faulty control module also can cause this fault code to be store.
  • damage or corroded can connector.

Symptoms :

  • some electronic control module will stop working.
  • warning lights will illuminate on the cluster meter.
  • fault code will store in engine control module.

Solution :

most of the time when this can fault code is store in control module JBE. check the can wiring harness behind the driver seat under carpet. due to water wiring harness get damage. repairing that wiring harness can solve the problem.

  • Repair damage wiring harness of K-CAN line.
  • Replace faulty control module.
  • repair damage con connector loop.
short can line behind the driver seat.

How to Diagnose K-CAN line fault :

  • Finding K-CAN fault can difficult to find but is may be easy if it would do step by step.
  • mechanic should start diagnosing this fault code with scanning the entire control module by taking heath report of vehicle. health report of vehicle will let you know that how many control module have the can line fault.
  • after finding that how many control module have can line fault, it will be easy to diagnose. like if the can line fault is only in rear side of all control module like EHC, TPMS, PDC. it is quit possible that the can connector loop at rear side may damage or short somewhere. if it indicate that can line is faulty or short at rear, check the loop of wire at rear right side below rear fuse box. the loop of can connector present in that loop always brake due to the water store at that area. and it is also possible that the internal failure of any one control module can cause this fault code to store.
  • If the can line fault is present in the front side control module like in instrument cluster, JBE , IHKA, radio, seats, gear selector switch. than it indicate that the can wiring harness is short or damage at front side. trace the loop of wire and find the can line loop check for brake of that loop, damage or short wiring of can.
  • in most of the cases when fault code store in front side control module. check the wiring of can line around dashboard , central console and around front seats. Because sometime mechanic use to remove dashboard and central console to do some work and when they fit that again it is possible that the can line wire may get stuck with any screw or dashboard. when this happen can line start sending wrong signal and this type of fault code may store. and also some time when one wire of can line is broken but the entire system will work without customer noticing.
  • Finding damage can line wire, or faulty control module may be easy by using oscilloscope. which indicate the signal of can line.
  • there are to wire in K-CAN line one is can high wire and other one is can low wire. the sum of voltage of both can wire is equal to 5V.
  • can low wire may have below 2.5 ( 0.4 – 2.0 ) volt and can high may have above 2.5 ( 2.5 – 4.0 ) volt. voltage may be vary in low or high can wire but the total voltage of low and high can wire should be 5 voltage.
  • if the entire wiring harness of can line is good and there is no any damage in wiring harness. check the can signal of faulty control module, disconnect faulty control module.

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