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Home >> GMC >> 1991 >> Value Van 7.4 N >> Repair and Diagnosis >> External Pages >> Different car >> Section 39 (Engine Controls - Tests W/Codes - 5.2L CNG) >> Self-Diagnostic Tests >> Test TC-7A - No Vehicle Speed Sensor Signal (DTC 15)

Test TC-7A - No Vehicle Speed Sensor Signal (DTC 15)

WARNING: This page is about a different car, the 1995 Dodge Ram Wagon, 1995 Dodge Ram Van, 1995 Dodge Pickup, and 1995 Dodge Dakota. However, it is still accessible from the selected car via links, so may be relevant.
  1. Raise vehicle on a hoist so wheels are free to spin. Start engine. Using scan tool, read Vehicle Speed Sensor (VSS) signal. Put transmission in Drive. If scan tool displays zero MPH, go to step 5). If scan tool displays more than zero MPH, condition required to set DTC is not present at this time.
  2. NO VEHICLE SPEED SENSOR SIGNAL DTC sets if Powertrain Control Module (PCM) does not see a speed signal on terminal No. 47 under road load conditions. Possible causes are: open or shorted VSS signal circuit (White/Orange wire), open 8-volt power supply circuit (Orange wire), open sensor ground circuit (Black/Light Blue wire), failed sensor, failed PCM, or failed Daytime Running Lights (DRL) module (if equipped).
  3. Inspect all related wiring and connectors, and repair as necessary. Perform TEST VER-2. If wiring and connectors are okay, condition that initially set DTC has just been simulated. Perform following additional checks to assist in identifying a possible intermittent problem.
  4. Visually inspect related wiring harness connectors for broken, bent, pushed-out or corroded terminals. Visually inspect related wiring harnesses for chafed, pierced or broken wires. Check all related Tech Service Bulletins (TSBs) and perform corrective action as necessary. Test is complete. Perform TEST VER-2.
  5. Turn ignition off. Disconnect and inspect Vehicle Speed Sensor (VSS) connector for damaged, pushed-out or miswired terminals. Repair as necessary. Perform TEST VER-2.
  6. If connector is okay, turn ignition on. Using scan tool in voltmeter mode, check voltage on VSS connector, 8-volt power supply circuit (Orange wire). If voltage is less than 7 volts, repair open in Orange wire. Perform TEST VER-2. If voltage is more than 7 volts, check voltage on VSS connector, VSS signal circuit (White/Orange wire) using scan tool.
  7. If voltage is less than 4 volts, go to TEST TC-7B. If voltage is more than 4 volts, connect a jumper wire to VSS connector, VSS signal circuit (White/Orange wire). Using scan tool, read VSS signal. While observing scan tool display, tap other lead of jumper to VSS connector, sensor ground circuit (Black/Light Blue wire).
  8. If scan tool does not display more than zero MPH, go to TEST TC-7B. If scan tool displays more than zero MPH, remove speed sensor. Inspect speedometer pinion gear. Repair as necessary. Perform TEST VER-2. If pinion gear is okay, replace VSS. Perform TEST VER-2.
  9. Put transmission in any forward gear. If scan tool displays more than zero MPH, go to next step. If scan tool does not display more than zero MPH, go to step 12).
  10. Condition required to set DTC is not present at this time. NO VEHICLE SPEED SENSOR SIGNAL DTC sets if Powertrain Control Module (PCM) does not see a VSS signal at PCM terminal No. 47 (White/Orange wire) under road load conditions. Possible causes are: open or shorted VSS signal circuit (White/Orange wire), no signal from Transmission Control Module (TCM) or failed PCM. Go to next step.
  11. Inspect all related wiring and connectors, and repair as necessary. Perform TEST VER-2. If no problems were found with wiring and connectors, see INACTIVE DTC CONDITION  . Perform TEST VER-2.
  12. Using scan tool, read Electronic Automatic Transmission (EATX) DTCs. If Code(s) 50-58 is displayed. If Code(s) 50-58 is not displayed, turn ignition off.
  13. Disconnect Transmission Control Module (TCM) connector. Turn ignition on. Using scan tool in voltmeter mode, check voltage on TCM connector terminal No. 58, Vehicle Speed Sensor (VSS) signal circuit (White/Orange wire). If voltage is more than 4 volts, go to step 17).
  14. If voltage is less than 4 volts, ensure ignition is off. Disconnect Powertrain Control Module (PCM) connector. Inspect PCM connector for damaged or pushed-out terminals. Repair as necessary. Perform TEST VER-2. If connector is okay, go to next step.
  15. Using an external ohmmeter, check resistance of signal circuit (White/Orange wire) between TCM connector terminal No. 58 and PCM connector terminal No. 47. If resistance is more than 5 ohms, repair open in White/Orange wire. Perform TEST VER-2.
  16. If resistance is less than 5 ohms, using scan tool in ohmmeter mode, check resistance of PCM connector terminal No. 47, signal circuit (White/Orange wire). If resistance is less than 5 ohms, repair short to ground in White/Orange wire. Perform TEST VER-2. If resistance is more than 5 ohms, replace PCM. Perform TEST VER-2.
  17. Using scan tool, read vehicle speed. Connect a jumper wire to TCM connector terminal No. 58 (White/Orange wire). While observing scan tool display, tap other end of jumper wire to ground. If scan tool displayed vehicle speed more than zero MPH, replace TCM. Perform TEST VER-2.
  18. If scan tool did not display more than zero MPH, turn ignition off. Disconnect Powertrain Control Module (PCM) connector. Using an external ohmmeter, check resistance of signal circuit (White/Orange wire) between TCM connector terminal No. 58 and PCM connector terminal No. 47.
  19. If resistance is less than 5 ohms, replace PCM. If resistance is more than 5 ohms, repair open in White/Orange wire. Perform TEST VER-2.
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