RAM 1500 Truck 2WD V6-3.9L VIN X (1999)
Short to 5 Volts - Either or both of the bus wires are shorted to a 5 volt potential.
Short to Ground - Either or both of the bus wires are shorted to ground.
Bus (+) & (-) Shorted Together - The two bus wires are shorted together.
No Termination - The bus system has lost connection with all of its terminators. The Instrument Cluster (MIC) and Powertrain Controller (PCM)
supply termination for the 1999 Ram Trucks.
Bus Bias Level Too Low - Either or both of the bus wire potentials are significantly below their normal 2.5 volts.
Bus Bias Level Too High - Either or both of the bus wire potentials are significantly above their normal 2.5 volts.
No Bus Bias - The bus system has lost connection with all modules that provide basis. The Instrument Cluster (MIC) provides the CCD bus bias for the
1999 Ram Trucks.
Bus (+) Open - The bus (+) wire has lost connection with termination and/or bias.
Bus (-) Open - The bus (-) wire has lost connection with termination and/or bias.
Not Receiving Bus Messages Correctly - The DRB cannot communicate over the bus and does not know why.
Vehicle Communication
Chrysler Collision Detection multiplex system (CCD) bus consists of a twisted pair of wires. These wires run from one module to another. They receive
and deliver coded information between the modules. The information is coded to identify the message as well as the importance of the message. Where
there are multiple messages trying to access the CCD bus at one time, the code determines the message that has the higher priority, and is then allowed to
access the bus first.
The tow wires of the twisted pair that make up the CCD multiplex system are called "bus +" (bus plus) and "bus -" (bus minus) respectively. Each wire
has a measurable voltage level of roughly 2.5 volts. In order to maintain the 2.5 volts on each line and provide a means of transportation for the coded
messages, there is a voltage divider network located in the module that supplies bus bias or voltage. Along with the module that supplies bias, some
modules provide termination. Bias is the voltage necessary to make the bus operational. At least one point of termination is necessary, some systems use
more than one. Some modules are capable of biasing and terminating the bus by themselves. Termination in the circuitry (a 20 ohm resistor placed
across the bus) is required to complete the voltage divider network circuit and also provide some electromagnetic protection for the bus. Without
termination, voltage on the bus goes approximately 5 volts on one wire and 0 volts on the other wire. In the 1999 Ram Truck, the instrument cluster
supplies bus bias and termination and the PCM supplies and additional point of termination.
NOTE: COMMUNICATION OVER THE BUS IS ESSENTIAL TO THE PROPER OPERATION OF THE VEHICLES ON-BOARD DIAGNOSTIC
SYSTEMS AND THE DRB. PROBLEMS WITH THE OPERATION OF THE BUS OR DRB MUST BE CORRECTED BEFORE PROCEEDING
WITH DIAGNOSTIC TESTING.
Wiper System
The Ram truck equipped with a high line CTM will utilize speed sensitive intermittent wipers. Only a high line CTM will be able to support this feature.
A base CTM (IEM) will provide for intermittent wipers without the speed sensitive feature. The low and high speeds are controlled through the wiper
stalk switch. The intermittent portion of the wiper control is handled by the CTM through the intermittent wiper relay. When the module detects a
decrease in delay time as selected by the driven an immediate wipe of the windshield takes place and the new delay interval is implemented. This feature
is present on both the base and highline CTM.
When the vehicle is moving at speeds at or below 10 mph, the delay time ranges from 1 to 36 seconds. When the speed rises above 10 mph, the delay
times are cut in half for a range of 1/2 to 8 seconds. The speed signal is provided to the CTM from the PCM over the CCD bus.
