DD15 Troubleshooting – Section 21.3 SPN 84/FMI 4

Section 21.3
SPN 84/FMI 4

This diagnostic condition is typically VSS circuit failed low.‪

Check for a short as follows:‪

1. Disconnect the VSS connector.
2. Disconnect the CPC #3 connector (21–pin).
3. Measure the resistance between pin 1 and pin 2 of the VSS harness connector.
   1. If the resistance measurement is less than 5 Ω, repair the short pin 13 and pin 14 of the CPC #3 connector (21–pin). Refer to "23.3.1.1 Verify Repairs" .
   2. If the resistance measurement is greater than 5 Ω, go to the next step.
4. Measure the resistance between pin 1 of the VSS harness connector and ground.
   1. If the resistance measurement is less than 5 Ω, repair the short to ground between pin 13 of the CPC #3 connector (21–pin) and pin 1 of the VSS harness connector. Refer to "23.3.1.1 Verify Repairs" .
   2. If the resistance measurement is greater than 5 Ω, go to the next step.
5. Measure the resistance between pin 2 of the VSS harness connector and ground.
   1. If the resistance measurement is less than 5 Ω, repair the short to ground between pin 14 of the CPC #3 connector (21–pin) and pin 2 of the VSS harness connector. Refer to "23.3.1.1 Verify Repairs" .
   2. If the resistance measurement is greater than 5 Ω, replace the VSS. Refer to "23.3.1.1 Verify Repairs" .

Section 21.3.1
Verify Repairs

Check for a short as follows:‪

1. Turn ignition OFF.
2. Reconnect any electrical connections that were disconnected to perform the diagnosis.
3. Clear codes with DDDL 7.0 or latest version.
4. Start and bring engine up to operating temperature (over 140°F/60°C).
5. Verify operation is satisfactory and no warning lamps illuminate. If warning lamps illuminate, troubleshoot the codes. If assistance is required, call the Detroit Diesel Customer Support Center at 313–592–5800.