Cooling System Diagnosis; Drb Scan Tool - Dodge ram truck 3500 1996 Service Manual

7 - 1 4 COOLING SYSTEM B R
DIAGNOSIS AND TESTING (Continued)
I f the problem Is sensed in a monitored circuit
often enough to indicate an actual problem, a DTC is
stored. The DTC will be stored In the PCM memory
for eventual display to the service technician. I f the
problem Is repaired or ceases to exist, the PCM can­
cels the DTC after 51 engine starts.
Certain criteria must be met for a DTC to be
entered Into PCM memory. The criteria may be a
specific range of engine rpm, engine temperature
and/or Input voltage to the PCM.
A DTC Indicates that the PCM has recognized an
abnormal signal in a circuit or the system. A DTC
may indicate the result of a failure, but never Iden­
tify the failed component directly.
It is possible that a DTC for a monitored circuit may
not be entered into memory even though a malfunction
has occurred. Refer to On- Board Diagnostics (OBD) in
Group 14, Fuel Systems for additional information.
ACCESSING DIAGNOSTIC TROUBLE CODES
A stored Diagnostic Trouble Code (DTC) can be dis­
played by cycling the ignition key On-Off-On-Off-On
within three seconds and observing the malfunction
indicator lamp. This lamp is displayed on the instru­
ment panel as the CHECK ENGINE lamp (Fig. 30).
They can also be displayed through the use of the
Diagnostic Readout Box (DRB) scan tool. The DRB con­
nects to the data link connector (Fig. 31) located at the
lower edge of instrument panel near the steering column.
For operation of the DRB, refer to the appropriate Pow-
ertrain Diagnostic Procedures service manual.
16-WAY DATA
LINK CONNECTOR
805dd852
Fig. 31 Data Link Connector
EXAMPLES:
• I f the lamp (Fig. 30) flashes 1 time, pauses and
flashes 2 more times, a flashing Diagnostic Trouble
Code (DTC) number 12 is indicated. I f this code is
observed, i t is indicating that the battery has been
disconnected within the last 50 key-on cycles. I t
could also indicate that battery voltage has been dis­
connected to the PCM. In either case, other DTCs
may have been erased.
• I f the lamp flashes 1 time, pauses and flashes 7
more times, a flashing Diagnostic Trouble Code
(DTC) number 17 is indicated.
After any stored DTC information has been observed,
the display will end with a flashing DTC number 55.
This will indicate the end of all stored information.
ERASING TROUBLE CODES
After the problem has been repaired, use the DRB
scan tool to erase a DTC. Refer to the appropriate
Powertrain Diagnostic Procedures service manual for
operation of the DRB scan tool.
DRB SCAN TOOL
For operation of the DRB scan tool, refer to the appro­
priate Powertrain Diagnostic Procedures service manual.
PRELIMINARY CHECKS
ENGINE COOLING SYSTEM OVERHEATING
Establish what driving conditions caused the com­
plaint. Abnormal loads on the cooling system such as
the following may be the cause:
(1) PROLONGED IDLE, VERY HIGH AMBIENT
TEMPERATURE, SLIGHT TAIL WIND AT IDLE,
SLOW TRAFFIC, TRAFFIC JAMS, HIGH SPEED
OR STEEP GRADES.
Driving techniques that avoid overheating are:
• Idle with A/C off when temperature gauge is at
end of normal range.
• Increasing engine speed for more air flow is rec­
ommended.
(2) TRAILER TOWING:
Consult Trailer Towing section of owners manual.
Do not exceed limits.
(3) AIR CONDITIONING; ADD-ON OR AFTER
MARKET:
A maximum cooling package should have been
ordered with vehicle i f add-on or after market A/C is
installed. I f not, maximum cooling system compo­
nents should be installed for model involved per
manufacturer's specifications.
(4) RECENT SERVICE OR ACCIDENT REPAIR:
Determine i f any recent service has been per­
formed on vehicle that may effect cooling system.
This may be:
• Engine adjustments (incorrect timing)
• Slipping engine accessory drive belt(s)
• Brakes (possibly dragging)
« Changed parts. Incorrect water pump or pump rotat­
ing in wrong direction due to belt not correctly routed
• Reconditioned radiator or cooling system refill­
ing (possibly under filled or air trapped in system).
NOTE: If investigation reveals none of the previous
items as a cause for an engine overheating complaint,
refer to following Cooling System Diagnosis charts.