32.1 SPN 168/FMI 0
This diagnosis is typically battery voltage high.
32.1.1
Measure Battery Voltage
Check as follows:
1. Measure battery voltage with the engine running at maximum rpm.
2. If greater than 16 volts, check for proper alternator operation and repair or replace, as
required. Refer to section 32.1.1.1.
32.1.1.1
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.
32.2 SPN 168/FMI 1
This diagnosis is typically battery voltage low.
32.2.1
Alternator and Battery Check
Check as follows:
1. Check the condition of the alternator drive belt and replace, if required.
[a] If fault is no longer active, refer to section 32.2.2.1.
[b] If fault is still active, go to step 2.
2. Check for loose alternator mounting and retighten or repair, as required.
[a] If fault is no longer active, refer to section 32.2.2.1.
[b] If fault is still active, go to step 3.
3. Check for proper alternator operation and repair or replace, as required.
[a] If fault is no longer active, erase fault code memory.
[b] If fault is still active, go to step 4.
4. Check the condition of the battery (does it hold the charge?) and replace, if required.
[a] If fault is no longer active, refer to section 32.2.2.1.
[b] If fault is still active, refer to section 32.2.2.
32.2.2
Measure the Resistance
Measure the resistance as follows:
1. Measure the resistance of the individual wires in the ground circuit (MCM 21/5, 21/6,
21/8, 21/9 and CPC 2/2). See Figure 32-1.
[a] If resistance is greater than 0.5 Ω in any wire, repair or replace the wire and
connector.Refer to section 32.2.2.1.
[b] If resistance is less than 0.5 Ω in all wires, go to step 2.
2. Measure the resistance of the individual wires in the power circuit (MCM 21/11, 21/12,
21/14, 21/15 and CPC 2/1) with the engine running and battery voltage greater than 12.5
V. See Figure 32-1.
[a]If resistance is greater than 0.5 Ω in any wire, repair or replace the power circuit
wires and connector. Refer to section 32.2.2.1.
[b] If resistance is less than 0.5 Ω in any wire, go to step 3.
3. Measure the current drop of the individual wires in the ground circuit (MCM 21/5, 21/6,
21/8, 21/9 and CPC 2/2). See Figure 32-1.
[a] If the current drop is more than 0.2 volts in any wire, repair or replace the ground
circuit wires and connector. Refer to section 32.2.2.1.
[b] If the current drop is less than 0.2 volts in any wire, go to step 4.
4.Measure the current drop of the individual wires in the power circuit (MCM 21/11, 21/12,
21/14, 21/15 and CPC 2/1).See Figure 32-1
[a] If the current drop is more than 0.2 volts in any wire, repair or replace the power
circuit wires and connector. Refer to section 32.2.2.1.
[b] If the current drop is more than 0.2 volts in any wire, refer to section 32.2.2.1.
32.2.2.1
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.
