SYS.OK|MANUAL.DB● LIVE
HOMESERVICE MANUALSGMC1999FORWARD CONTROL 4.3 W, STANDARDREPAIR AND DIAGNOSISBRAKESTRACTION CONTROLANTI-LOCK BRAKE SYSTEMDIAGNOSIS & TESTINGDIAGNOSTIC SYSTEM CHECKDIAGNOSIS
1999 GMC Forward Control 4.3 W, Standard

Diagnostic System Check: Diagnosis

1999 GMC Forward Control 4.3 W, StandardSECTION Diagnosis
  1. Verify all EBCM connectors are connected properly. Install scan tool. Turn ignition switch to RUN position. Using scan tool, try to communicate with the EBCM. If data is being received from EBCM, go to next step. If data is not received from EBCM, go to step 4)  .
  2. Using the scan tool, record any current or history DTCs. If any DTCs are present, see 4WAL DIAGNOSTIC TROUBLE CODE (DTC)  table. If DTC(s) are not present, go to next step.
  3. Turn ignition off for 10 seconds. Turn ignition switch to RUN position and observe the ABS indicator lamp. If the lamp is on for 3 seconds then goes out, the system is operating normally. If not, go to step 11)  .
  4. Turn ignition off. Disconnect the 10-way EBCM harness connector. Turn ignition switch to RUN position. Measure voltage between EBCM harness connector terminal A and ground. If the voltage is between 10-15 volts, go to next step. If not, go to step 9)  .
  5. Disconnect negative battery terminal. Disconnect 10-pin EBCM harness connector. Check resistance between negative battery terminal and 10-pin EBCM harness connector terminal "J". If resistance is 0-2 ohms, go to next step. If resistance is not 0-2 ohms, go to step 12)  .
  6. Inspect EBCM and EBCM harness connector terminals for poor contact. Inspect battery terminals and battery cable terminals for poor connection. Repair as necessary. Is there a poor connection, then go to next step. If connections or terminals are okay, go to step 8)  .
  7. Repair the poor connection. After repairs, go to step 1)  .
  8. Reconnect EBCM harness connectors and battery terminals. If communications cannot be established between scan tool and EBCM, try scan tool on similar vehicle with the same system to determine if scan too is malfunctioning or if Class 2 data line is faulty. See DATA LINK COMMUNICATIONS SYSTEM CHECK in appropriate DATA LINK COMMUNICATIONS article. Repair or replace as necessary.
  9. Disconnect positive battery cable. Turn ignition switch to RUN position. Measure resistance between the positive battery cable and terminal "A" of the EBCM. If the resistance is 0-2 ohms, go to next step. If not, go to step 13)  .
  10. Turn ignition off. Remove 10 amp ABS/Brake fuse. Measure resistance between EBCM terminal "A" and ground. If the resistance is infinite, go to step 15)  . If not, go to step 14)  .
  11. Observe the ABS light. If ABS light stays on, go to step 18)  . If not, go to step TEST A: ANTI-LOCK LIGHT DOES NOT ILLUMINATE - NO DTCS  under DIAGNOSIS & TESTING.
  12. Repair open or high resistance in circuit No. 451. After repairs, repeat step 1)  .
  13. Repair open or high resistance in circuit No. 441. Check 10 amp ABS/Brake fuse. After repairs, repeat step 1)  .
  14. Repair short to ground in circuit No. 441. Check circuit breaker. After repairs, repeat step 1)  .
  15. Inspect ignition and brake switch input circuits and 10-pin EBCM harness connector C1 for physical damage, which could cause a short to ground with EBCM harness connector connected to EBCM. Repair as necessary. If damage is found, go to step 16)  . If no damage is found, go to step 17)  .
  16. Repair damaged terminals. After repairs, go to step 1)  .
  17. Check 10-amp ABS/Brake fuse. If the fuse is good, replace the EBCM. After repairs, repeat step 1)  .
  18. Use scan tool to turn off the ABS light. If the light goes off, go to next step. If not, go to step 20)  .
  19. Replace the instrument cluster. After repairs, repeat step 1)  .
  20. Replace EBCM. After repairs, repeat step 1)  .
RENDER: 1.0x

NO RELATED

Recommended Tools & Savings

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Affiliate disclosure: We may earn a commission at no extra cost to you.

Shop Manual-Ready ToolsFree Quote CheckQuote Shield Pro

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.