23.1 SPN 84/FMI 2
Contact the Detroit Diesel Support Center at 313–592–5800.
23.2 SPN 84/FMI 3
This diagnostic condition is typically VSS open circuit.
23.2.1
Open Circuit Check
Check as follows:
1. Disconnect the Vehicle Speed Sensor (VSS).
2. Measure the resistance between pin 13 of the CPC connector #3 (21–pin) and pin 1 of the VSS.
[a] If the resistance is greater than 3 Ω, repair the open between pin 13 of the CPC connector #3 (21–pin) and pin 1 of the VSS. Refer to section 23.2.1.1.
[b] If the resistance is less than 3 Ω, go to step 3.
3. Measure the resistance between pin 14 of the CPC connector #3 (21–pin) and pin 2 of the VSS sensor.
[a] If the resistance is greater than 3 Ω, repair the open wire between pin 14 of the CPC #3 connector (21–pin) and pin 2 of the VSS. Refer to section 23.2.1.1.
[b] If the resistance is less than 3 Ω, go to step 4.
4. Measure the resistance between pin 13 of the CPC connector #3 (21–pin) and pin 1 of the VSS sensor.
[a] If the resistance greater than 3 Ω, replace the VSS. Refer to section 23.2.1.1.
[b] If the resistance is less than 3 Ω, repair the short in the harness between pins 13 and 14 of the CPC connector #3 (21–pin). Refer to section 23.2.1.1.
23.2.1.1
Verify Repairs
Verify repairs 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.
23.3 SPN 84/FMI 4
This diagnostic condition is typically VSS circuit failed low.
23.3.1
Short Circuit Check
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.
[a] 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 section 23.3.1.1.
[b] If the resistance measurement is greater than 5 Ω, go to step 4.
4. Measure the resistance between pin 1 of the VSS harness connector and ground.
[a] 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 section 23.3.1.1.
[b] If the resistance measurement is greater than 5 Ω, go to step 5.
5. Measure the resistance between pin 2 of the VSS harness connector and ground.
[a] 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 section 23.3.1.1.
[b] If the resistance measurement is greater than 5 Ω, replace the VSS. Refer to section
23.3.1.1.
23.3.1.1
Verify Repairs
Verify repairs 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.
23.4 SPN 84/FMI 6
Contact the Detroit Diesel Support Center at 313–592–5800.
23.5 SPN 84/FMI 8
Contact the Detroit Diesel Support Center at 313–592–5800.
