TM 9-2320-363-20-1
Section 4
TROUBLESHOOTING CHARTS
A. THE DIAGNOSTIC PROCEDURE - WHERE TO START
When diagnosing the cause for engine performance, fuel economy or exhaust system complaints, perform normal
checks (non DDEC-III items) before considering DDEC as the possible source of the problem.
When diagnosing the system, always start with the first chart (labeled "START) on page 3-345.41. 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 the "Customer Complaint"
chart 1 on page 3-345.57, 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 III DIAGNOSTIC CODES/WHAT THEY MEAN
The following pages give a brief description of each diagnostic code. Basic facts about these codes are given below:
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.
If a problem goes away, the "Check Engine" light will turn off. But the code will remain stored in the ECM.
Code 25 means no codes were stored at all.
FLASH CODE:
11
DDR DISPLAY:
VSG SENSOR INPUT VOLTAGE LOW
SAE J1587 CODE:
PID: 187 FMI: 4
Indicates that the Variable Speed Governor (VSG) input to the ECM has dropped below 5% (normally < 0.25 volts)
of the sensor supply voltage. 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.
VSG SENSOR INPUT VOLTAGE HIGH
SAE J1587 CODE:
PID: 187 FMI: 3
Indicates that the Variable Speed Governor (VSG) 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
Change 3 3-345.19
