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Code 34, Abs Valve Relay

  1. Turn ignition off. Unplug ABS/AWD control unit. Check continuity between pins No. 20 and 7 of ABS/AWD control unit wiring harness for an open circuit or a short circuit to ground or battery voltage. If circuit is okay, go to step 4).
  2. If circuit is open or shorted to ground or battery voltage, remove ABS valve relay. Check continuity between pin No. 7 of ABS/AWD control unit wiring harness and pin No. 85 of ABS valve relay base. See Figure .
  3. Also check continuity between pin No. 20 of ABS/AWD control unit wiring harness and pin No. 86 of ABS valve relay base. If wiring harness is okay (not open or shorted), replace ABS valve relay.
  4. Check resistance between pins No. 2 and 17, pins No. 17 and 19, and between pins No. 17 and 22 of ABS/AWD control unit wiring harness. Resistance should be 1-2 ohms.
  5. Also check resistance between pins No. 18 and 23 and between pins No. 21 and 23. Resistance should be 2-4 ohms. If resistances are correct, go to step 8). If resistances are incorrect, determine if fault is in wiring harness or ABS/differential locking valves.
  6. Remove 12-pin connector from ABS hydraulic control unit. Check resistance of ABS solenoid valves between pins No. 1 and 4, pins No. 3 and 4, and between pins No. 5 and 4 of ABS hydraulic control unit. See Fig 1 . Resistance should be 0.7-1.7 ohms. If resistance is incorrect, replace ABS hydraulic control unit.
    Fig 1: Identifying ABS Hydraulic Unit 12-Pin Connector
    G93H82690Courtesy of PORSCHE OF NORTH AMERICA, INC.
  7. Unplug connector from valve block assembly. Measure resistance of differential locking valves between pins No. 1 and 3 and between pins No. 2 and 4 on valve block assembly. See Figure . If resistance is not 2-4 ohms, replace valve block assembly.
  8. Remove 7-pin ABS valve relay from ABS hydraulic control unit. Check for a short circuit to ground or battery voltage at pin No. 17 of ABS/AWD control unit wiring harness. If necessary, unplug ABS hydraulic control unit to help isolate short circuit. Repair circuit as necessary.
  9. Ensure battery voltage is present at pin No. 87 of ABS valve relay base. See Figure . If battery voltage is not present, repair circuit as necessary.
  10. Using a Digital Volt-Ohmmeter (DVOM), measure resistance between pin No. 87a on ABS relay base and ground wire at ABS hydraulic control unit. Resistance should be 2-4 ohms. If resistance is incorrect, replace ABS hydraulic control unit (resistor in relay base is faulty).
  11. Check for an open circuit between pin No. 24 of ABS/AWD control unit wiring harness and pin L1 of ABS valve relay base. Also check for an open circuit between pin No. 35 of control unit and pin L2 of base. Repair circuit as necessary.
  12. Reconnect all disconnected components. Push back protective cap at valve block assembly connector. Turn ignition off, then back on. Ensure voltage is present at pin No. 1 and 2 (ABS valve relay energized). If no voltage is present, replace ABS valve relay. If voltage is present and ABS valve relay is okay, replace ABS/AWD control unit.
NOTE: If Bosch ABS-2 LED Tester (KDAS 0003) is available, test valve relay. Using tester, in switch position 5, will ensure relay is genuinely defective. If LED on tester fails to light up steadily with ignition on, relay is defective.
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