Section 4
TROUBLESHOOTING CHARTS
TM 9-2320-363-20-1
A. THE DIAGNOSTIC PROCEDURE l WHERE TO START
When diagnosing the cause for engine performance. fuel economy or exhaust system complaints, perform normal checks
(non DDEC II equipped engine) before considering DDEC II as the possible source of the problem.
When diagnosing the system, always start with the first chart (labelled “START”) on Page 3-121. This will utimately lead
to other diagnostic charts, even in the cases where no codes were logged but a symptom(s) was noted. In fact, if no
codes were recorded (but a symptom remains), the “START” chart will refer you to the “Customer Complaint” Chart 1,
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. DIAGNOSTIC CODES l 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.
Code 13
Code 14
Code 15
Code 16
Code 21
Code 22
Code 23
Code 24
Coolant Level Sensor (CLS) - System running for 2 seconds with too low a voltage at the ECM input. Battery
voltage at the ECM must also be greater than 11 volts.
Oil or Coolant Temperature Sensor (OTS or CTS) - Engine running for 8 minutes with too high a voltage at the
OTS or CTS input to the ECM.
Oil or Coolant Temperature Sensor (OTS or CTS). Engine running for 2 seconds with too low a voltage at the
OTS or CTS input to the ECM.
Coolant Level Sensor (CLS) - System running for 2 seconds with too high a voltage at the ECM input. Battery
voltage at the ECM must also be greater than 11 volts.
Throttle Position Sensor (TPS) - System running for 2 seconds with too high a voltage at the TPS input to the ECM.
Throttle Position Sensor (TPS) - System running for 2 seconds with too low a voltage at the TPS input to the ECM.
Fuel Temperature Sensor (FTS) - Engine running for 8 minutes with too high a voltage at the FTS input to the ECM.
Fuel Temperature Sensor (FTS) - Engine running for 2 seconds with too low a voltage at the FTS input to the ECM.
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