1-secm-03-77.pdf - flash code 77 - freightliner trucks · pdf file77.2 sae j1587 equivalent...

77 FLASH CODE 77 - EXHAUST BACK PRESSUREFAULT AND SEVERAL INFORMATION CODES

Section Page

77.1 DESCRIPTION OF FLASH CODE 77 ...................................................... 77-3

77.2 SAE J1587 EQUIVALENT CODE FOR FLASH CODE 77 ....................... 77-3

77.3 TROUBLESHOOTING FLASH CODE 77 ................................................ 77-5

Figure 77-1 ECM

(Rev. 2/03) All information subject to change without notice.

77-2 From Bulletin 1-SECM-03 6SE497 0207 Copyright © 2003 DETROIT DIESEL CORPORATION

DDEC III/IV SINGLE ECM TROUBLESHOOTING GUIDE

77.1 DESCRIPTION OF FLASH CODE 77

Flash Code 77 is used for several DDEC information codes. The codes are listed in Table 77-1.

At this time, this code is logged without illuminating a CEL.

See Figure 77-1 for ECM.

77.2 SAE J1587 EQUIVALENT CODE FOR FLASH CODE 77

The SAE J1587 equivalent codes for Flash Code 77 are listed in Table 77-1:

PID Description Troubleshooting

p 73 1 Fire pump pressure below rangeIndicates the water pump pressure fell below a calibratedvalue.

No troubleshooting available forthis code.Possible faults could be restrictedwater supply of failing pump.

p 81 0 Exhaust back pressure above range

p 81 1 Exhaust back pressure below range

Indicates the exhaust backpressure measured was above(FMI 0) or below (FMI 1) acalibrated value.Back pressure too high is usuallya sign of a restricted exhaust orfailing muffler/converter.

p 81 12 Exhaust back pressure at rampdown threshold Indicates the engine derated dueto high exhaust back pressure.This could have been presentedas a sudden power loss.This code is not a DDEC fault andshould be treated as a informationcode only.

p 81 3 Exhaust back pressure failed high

p 81 4 Exhaust back pressure failed low

Indicates the signal voltage tothe ECM went above or below aprogrammed limit. Typically, lessthan 25 V for FMI 4 and greaterthan 4.75 V for FMI3.Refer to section 77.3.1fortroubleshooting.

p 95 1 Fuel filter differential pressure below range

p 99 1 Oil filter differential pressure below range

Fuel filter or oil filter differentialpressure sensor fell belowcalibrated limit. Not likely to showup on any on-highway engines.These sensors are used as part ofthe Maintenance Alert System.

All information subject to change without notice. (Rev. 2/03)

6SE497 0207 Copyright © 2003 DETROIT DIESEL CORPORATION From Bulletin 1-SECM-03 77-3

77.2 SAE J1587 EQUIVALENT CODE FOR FLASH CODE 77


p 100 0 Engine oil pressure above range Indicates that DDEC detectedoil pressure too high followingshutdown. Typically, this iscaused by a stuck sensor. Thecode is generated on the nextignition cycle and stays active forthe duration of the ignition cycle.

p 102 1 Turbo boost pressure below range

p 105 1 Inlet manifold temperature below range

p 107 1 Air filter differential pressure below range

Indicates one of these parametersfell below a calibrated limit. Detailsof these codes should be recordedand technical service contacted,since it is unlikely these codes willbe used on highway engines.

p 108 0 Barometric pressure above range

p 108 1 Barometric pressure below range

Currently these codes should notlog with on-highway engines.

p 109 0 Coolant pressure above range Not used for Series 50 or Series60.

p 110 1 Coolant temperature below range

p 111 0 Coolant level above range

Neither of these codes should beseen for on-highway engines.

p 171 0 Ambient air temperature above range

p 171 1 Ambient air temperature below range

Neither of these codes should beseen for on-highway engines.

p 172 1 Air inlet temperature below range

p 174 0 TCO temperature above range (temporary code) Refer to code/section 49 – 404 0.

p 174 0 Fuel temperature above range Indicates fuel temperatureexceeded DDC limits forthat particular engine. NoDDEC troubleshooting issuggested. High fuel temperatureshould be reviewed with theOEM to determine if anyadditional fuel coolers need to beconsidered.

p 174 1 TCO temperature below range (temporary code) Refer to code/section 48 – 404 1.

p 174 1 Fuel temperature below range Indicates the fuel temperaturefell below a calibrated range. Notroubleshooting is suggest.

p 175 1 Engine oil temperature below range Indicates the engine oiltemperature fell below a calibratedrange. No troubleshooting issuggest.

p 222 14 Anti theft fault present Contact DDC Technical Service.





p 251 10 Clock module abnormal rate of change

p 251 13 Clock module failure

p 252 10 Clock module abnormal rate of change

p 252 13 Clock module failure

Codes indicate internal faults withthe clock components.Contact DDC Technical Service.

p 354 0 Relative humidity above range

p 354 1 Relative humidity below range

Currently, these codes should notlog with on-highway engines.

Table 77-1 Flash Code 77

77.3 TROUBLESHOOTING FLASH CODE 77

There is an established procedure to troubleshoot Flash Code 77, p 81/3 and p 81/4 only (exhaustback pressure failed high or low). Refer to section 77.3.1. There is no established procedureto troubleshoot other variations of this code.

The code is used to determine if high fuel temperature may be a cause of reduced powerlevels.High fuel temperature will reduce available horsepower.Refer to the recommendations of the vehicle manufacturer regarding the possible need foradditional fuel cooling.

77.3.1 Exhaust Back Pressure Fault

Follow these steps to troubleshoot an exhaust back pressure fault:

1. If code 81/3 displays, refer to section 77.3.2.

2. If code 81/4 displays, refer to section 77.3.6.

77.3.2 Exhaust Back Pressure Failed High

Follow these steps to troubleshoot exhaust back pressure failed high:

1. Disconnect exhaust back pressure sensor.

2. Start and run the engine.

3. Check codes displayed.

[a] If code 81/3 displays, refer to section 77.3.3.

[b] If code 81/4 displays, refer to section 77.3.5.

77.3.3 Check for Short to +5 Line

Follow these steps to check for a short to the +5 volt line:

1. Unplug the ECM vehicle connector.




2. Measure resistance between cavities B and C. See Figure 77-2.

Figure 77-2 Engine Temperature and Back Pressure Sensor WiringSchematic

[a] If the resistance measures greater than 5 , refer to section 77.3.4.




[b] If the resistance measures less than 5 , wire #916 is shorted to #510. Repair theshort and test.

77.3.4 Check for Open

Perform the following steps to check for open:

1. Install jumper between cavities A3 and C3.

2. Measure resistance between cavities A and C of the BPS connector.If measured resistance is less than 50 , refer to section 77.3.5.If measured resistance is greater than 50 , wire #952 is open. Repair the openand test.

77.3.5 Check Connectors

Perform the following steps to check the connectors:

1. If connectors are not damaged, replace the Backpressure Sensor. Test.

2. If the connectors are corroded, bent, or damaged, repair or replace them. Test.

77.3.6 Exhaust Back Pressure Sensor (BPS) Failed Low

Perform the following steps to troubleshoot this condition:

1. Unplug BPS.

2. Install a jumper cable between cavities A and B.

3. Start engine.If code 81/3 displays, refer to section 77.3.7.If code 81/4 displays, wire #510 is open. Repair the open and test.




77.3.7 Check for Short

1. Remove jumper cable.

2. Measure continuity between cavities B and C.If measured continuity is greater than 50 , refer to section 77.3.8.If measured continuity is less than 50 , wire #510 is shorted to wire #952. Repairthe short and test.

77.3.8 Check Connectors

Perform the following steps to check the connectors:

1. If connectors are not damaged, replace the Back Pressure Sensor. Test.

2. If the connectors are corroded, bent, or damaged, repair or replace them. Test.



1-secm-03-77.pdf - flash code 77 - freightliner trucks · pdf file77.2 sae j1587 equivalent...

Documents