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TM9-2320-360-20-3
Section 4
TROUBLESHOOTING CHARTS
A. THE DlAGNOSTlC PROCEDURE - WHERE TO START
When diagnosing the cause for engine performance, fuel economy or exhaust system complaints, perform Vehicle Trou-
bleshooting (Chapter 2) before considering DDEC as the possible source of the problem.
When diagnosing the system, always start with the first chart (labeled “START”) on page H-25. This will ultimately lead to
other diagnostic charts, even in the cases where no fault codes were logged but a symptom(s) was noted. In fact, if no
faults were recorded (but a symptom remains), the “START” chart will refer you to “Diagnosis by Symptom”, Chart 1, on
page H-40, which can identify fault trees to use based on the customer complaint.
NOTICE:
Although there are many charts connected with diagnostics, only one is needed to determine that the
system is operating properly Normally, only two charts are necessary to find a problem.
B. DDEC Ill DlAGNOSTlC CODES/WHAT THEY MEAN
The following pages give a brief description of each diagnostic code. Basic facts about these codes are given below:
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Most problems must occur for a total of at least two (2) seconds before the “Check Engine” light comes on and a code is
stored.
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If a problem goes away, the “Check Engine” light will turn off. But the code will remain stored in the ECM.
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Code 25 means no codes were stored at all.
FLASH CODE:
11
DDR DISPLAY
PTO SENSOR INPUT VOLTAGE LOW
SAE J1587 CODE:
PID: 187 FMI: 4
Indicates that the PTO input to the ECM has dropped below 5% (normally < 0.25 volts) of the sensor supply volt-
age. This diagnostic condition is typically:
(1) open sensor signal circuit
(2) open sensor +5 volt supply circuit
(3) sensor signal is shorted to the sensor return circuit or to ground
(4) sensor +5 volt supply is shorted to sensor return circuit or to ground
FLASH CODE:
12
DDR DISPLAY
PTO SENSOR INPUT VOLTAGE HIGH
SAE J1587 CODE:
PID: 187 FMI: 3
Indicates that the PTO input to the ECM has exceeded 95% (normally > 4.75 volts) of the sensor supply voltage.
This diagnostic condition is typically:
(1) open sensor return circuit
(2) sensor signal circuit is shorted to the sensor +5 volt supply
H-15
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