Series 60 DDEC V Troubleshooting – Section 72.3 Troubleshooting Flash Code 77, PID 81, FMI 4

Section 72.3
Troubleshooting Flash Code 77, PID 81, FMI 4

Flash Code 77, p 81/4 is exhaust back pressure failed low‪

Section 72.3.1
Exhaust Back Pressure Sensor Failed Low

Perform the following steps to troubleshoot this condition: ‪

1. Unplug EBP Sensor.
2. Install a jumper cable between cavities A and B.
3. Start engine.
   1. If code p 81/3 displays, refer to "72.3.2 Check for Short" .
   2. If code p 81/4 displays, wire #510 is open. Repair the open and refer to "72.3.3.1 Verify Repairs" .

Section 72.3.2
Check for Short

‪

1. Remove jumper cable.
2. Measure continuity between cavities A and C.
   1. If measured continuity is greater than 50 Ω, refer to "72.3.3 Check Connectors" .
   2. If measured continuity is less than 50 Ω, wire V-29 is shorted to wire V-60. Repair the short and refer to "72.3.3.1 Verify Repairs" .

Section 72.3.3
Check Connectors

Perform the following steps to check the connectors: ‪

1. If connectors are not damaged, replace the EBP Sensor and refer to "72.3.3.1 Verify Repairs" .
2. If the connectors are corroded, bent, or damaged, repair or replace them and refer to "72.3.3.1 Verify Repairs" .

‪

Section 72.3.3.1
Verify Repairs

Perform the following steps to verify repairs.‪

1. Turn ignition switch OFF and reconnect all connectors.
2. Turn ignition ON and clear codes.
3. Start and run the engine for one minute.
4. Stop the engine and check diagnostic tool for codes.
   1. If no codes are logged, no further troubleshooting is required.
   2. If codes p 81/4 was not logged, and other codes are logged, refer to "18.3 First Step for Diagnosing a Fault Within the DDEC System" .
   3. If code p 81/4 and other codes are logged, review this section from the first step to find the error.