LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Cadillac >> 2000 >> DeVille Base >> Repair and Diagnosis >> Steering >> Steering Column >> Memory Systems >> Diagnostic Tests >> DTC B1850: Driver Lumbar Horizontal Sensor Circuit Malfunction >> Diagnostic Procedure
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Diagnostic Procedure

  1. If power seats diagnostic system check was performed, go to next step. If power seats diagnostic system check was not performed, go to POWER SEATS DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC TESTS.
  2. Connect scan tool to Data Link Connector (DLC). See Figure . Turn ignition on. Using scan tool, select MEMORY SEAT MODULE SENSOR data list. Monitor LUMBAR HORIZONTAL SENSOR parameter. If LUMBAR HORIZONTAL SENSOR parameter is 0.25-4.75 volts, check for intermittent or poor connections at lumbar horizontal position sensor. If LUMBAR HORIZONTAL SENSOR parameter is not 0.25-4.75 volts, go to next step.
  3. Turn ignition off. Disconnect lumbar horizontal sensor. See Figure . Turn ignition on. Monitor LUMBAR HORIZONTAL SENSOR parameter. If LUMBAR HORIZONTAL SENSOR parameter is less than 0.25 volt, go to next step. If LUMBAR HORIZONTAL SENSOR parameter is greater than 0.25 volt, go to step  10 .
  4. Turn ignition off. Connect a 3-amp fused jumper wire between lumbar sensor connector terminal "A" (Yellow wire) and "B" (Gray wire). Turn ignition on. If LUMBAR HORIZONTAL SENSOR parameter is greater than 4.75 volts, go to next step. If LUMBAR HORIZONTAL SENSOR parameter is less than 4.75 volts, go to step  8 .
  5. Disconnect fused jumper wire. Using DVOM, measure voltage between lumbar sensor connector terminal "B" (Gray wire) and "C" (Black wire). If voltage is less than 5.50 volts, go to next step. If voltage is greater than 5.50 volts, go to step  7 .
  6. Turn ignition off. Disconnect negative battery cable. Using DVOM, measure resistance between ground and lumbar sensor connector terminal "C" (Black wire). If resistance is greater than 5 ohms, go to step  11 . If resistance is less than 5 ohms, go to step  12 .
  7. Check for short to voltage in Gray wire between lumbar horizontal position sensor and 4-pin connector C314 terminal "G". Connector C314 is located under left front seat. See Figure . If circuit is okay, go to step  13 . If faulty circuit is found and repaired, go to step  16 .
  8. Check for open, short to ground or high resistance in Gray wire between lumbar horizontal position sensor and 4-pin connector C314 terminal "G". Connector C314 is located under left front seat. See Figure . If circuit is okay, go to next step. If faulty circuit is found and repaired, go to step  16 .
  9. Check for open, short to ground or high resistance in Yellow wire between lumbar horizontal position sensor and Memory Seat Module (MSM) connector C2 terminal F3. See Figure . If circuit is okay, go to step  13 . If faulty circuit is found and repaired, go to step  16 .
  10. Check for short to voltage in Yellow wire between lumbar horizontal position sensor and Memory Seat Module (MSM) connector C2 terminal F3. See Figure . If circuit is okay, go to step  13 . If faulty circuit is found and repaired, go to step  16 .
  11. Disconnect Memory Seat Module (MSM) connector C2. See Figure . Check for high resistance or open in Black wire between lumbar horizontal position sensor and 4-pin connector C314 terminal "E". Connector C314 is located under left front seat. See Figure . If circuit is okay, go to step  13 . If faulty circuit is found and repaired, go to step  16 .
  12. Check for poor connections at lumbar horizontal sensor connector. If connections are okay, go to step  14 . If faulty connections are found and repaired, go to step  16 .
  13. Check for poor connections at MSM connector C2. If connections are okay, go to step  15 . If faulty connections are found and repaired, go to step  16 .
  14. Replace seat lumbar horizontal sensor. See SEAT MOTORS under REMOVAL & INSTALLATION in POWER SEATS - DEVILLE article. After repairs, go to step  16 .
  15. Replace MSM. See MEMORY SEAT MODULE  under REMOVAL & INSTALLATION. After repairs, go to next step.
  16. Use scan tool to clear DTCs. Recheck operation of driver's power lumbar. Recheck for DTC. If DTC resets, go to step  2 . If DTC does not reset, repair is complete.
scientia non olet · About LEMON Manuals