This diagnosis typically coolant level low.
30.1.1
Engine Coolant Level Sensor Check
Check as follows:
1. Turn the vehicle ignition switch ON (key On, engine OFF).
2. Check for multiple codes.
[a] If other faults are active in addition to fault 111/1, troubleshoot the other faults first.
[b] If only fault 111/1 is active, go to step 3.
3. Check the coolant level in the reservoir. See Figure 30-1.
[a] If the coolant level in the reservoir is not within limit, refer to section 30.1.2.
[b] If the coolant level in the reservoir is within limit, replace the sensor (see Figure 30-2). Refer to section 30.1.2.1.
30.1.2
Coolant Leak or Faulty Radiator Cap Check
Check as follows:
1. Check for coolant leak at cylinder head gasket.
2. Check for coolant leak at air compressor head gasket.
3. Check for external coolant leak at hose connections.
4. Check for coolant in oil.
5. Check for loose or faulty radiator cap.
6. When these checks and subsequent repairs are finished, Refer to section 30.1.2.1.
30.1.2.1
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.
