Section 56.1
SPN 636/FMI 1

The diagnostic condition is typically CKP Sensor Signal Voltage Too Low.‪

Section 56.1.1
Low Signal Voltage Check

Check low signal voltage as follows:‪

1. If fault occurs only when cranking the engine (and engine will not start), check that the CKP and Camshaft Position (CMP) sensors are correctly wired to the MCM. See Figure "Crankshaft Position Sensor Wiring" .
   

   Figure 1. Crankshaft Position Sensor Wiring

   1. If wires are not correctly wired, repair or replace wires as required. Refer to "56.1.1.1 Verify Repairs" .
   2. If wires are correctly wired, go to step 2 .
2. If fault occurs at other times then when cranking the engine, check that the CKP Sensor position is correct (the sensor is seated in all the way).
   1. If fault is not active after checking CKP Sensor position, repair the CKP Sensor clamping sleeve. Refer to "56.1.1.1 Verify Repairs" .
   2. If fault is still active after checking the CKP Sensor position, go to step 3 .
3. Check the flywheel position through the inspection window of the timing case using turning tool. Look for timing marks and damage.
   1. If the flywheel is out of position, repair or replace, as required. Refer to "56.1.1.1 Verify Repairs" .
   2. If the flywheel is not out of position, go to step 4 .
4. Check crankshaft axial play.
   1. If axial play is not within specifications, repair or replace crankshaft thrust bearings, as required. Refer to "56.1.1.1 Verify Repairs" .
   2. If axial play is within specifications, replace the MCM. Refer to "56.1.1.1 Verify Repairs" .

Section 56.1.1.1
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.