Part 2 of 2
Interior LightingThe courtesy lights are controlled by the [1][2]CTM. The door switches are inputs to the CTM and the courtesy lights are outputs. The glove box lamp and the ash receiver lamp (if equipped) are not controlled by the CTM. They are hardwired to individual switches and fuses. The ignition key halo lamp is controlled by the CTM and will remain ON for thirty seconds after the door is closed.
The highline [1][2]CTM also provides for illuminated entry option. If the CTM detects an unlock signal from the RKE transmitter, a door disarm switch input or the door jamb switch input, the interior courtesy lights will be turned ON. The illuminated entry function is canceled if the CTM senses and ignition "ON" condition or the "lock" command from a valid key fob.
If a door is left open or the dome lamp switch is left in the "ON" position for more than fifteen minutes, the [1][2]CTM will extinguish the lamps to avoid discharging the battery. If the lamps are turned ON by rotation of the headlamp panel dimmer switch, the CTM will not be able to turn them OFF.
Mechanical Instrument Cluster (MIC)
The Ram Truck MIC is available in only one version. The lowline cluster has seventeen indicators lamps and the highline has eighteen indicators lamps. The gauges are positioned with information received by the cluster over the CCD bus from the PCM. Some of the warning lamps are hardwired and the cluster using the CCD bus information controls some. The MIC is hardwired to the [1][2]CTM to provide the warning lamp announcement chimes.
There is a self test available for the cluster that will actuate all the gauges at their calibration points. The test will not run if the cluster sees engine RPM or vehicle speed. This test will light all CCD controlled lamps for verification of lamp operation. It also forces the odometer vacuum fluorescent display (VFD) to perform a segment check. The self test routine can be entered by pushing and holding the trip reset button while rotating the ignition key from the "OFF" to the "ON" position. When the word "chec" appears release the knob and the test will continue.
Starting in the 2000 Powertrain Control Module diagnostic trouble codes (P-Codes) will be displayed in the cluster odometer for the gas trucks only. A diagnostic trouble code display request will be initiated by the JTEC after 3 successive ignition cycles from "OFF" to "RUN" position. The cluster will display the received four digit P-Code for 4 seconds, then display 6 dashes and another P-Code. At the end, when all the P-Codes are done, the cluster will display "DONE" on the odometer.
The cluster will provide bus bias and termination and the engine controller provides a second termination. If the cluster is disconnected the bus will not be biased.
The cluster will be service as an assembly. There will be limited parts available, bulbs and sockets, the front lens, the trip odometer stem cover and the rear cover assembly. No internal parts of the cluster will be serviced.
Normal Operations
At key ON, the cluster will light the low fuel, seat belt, check gauges, and airbag. As the key is turned farther towards the start position, the check engine, ABS (if equipped) and brake warning lamp will illuminate. The (VFD) will indicate the mileage stored inside the cluster. If there is a bus failure and the cluster cannot receive distance pulses from the engine controller, the cluster will display the last mileage stored until the ignition is turned OFF. If the cluster is receiving bus messages but is unable to display odometer information because of an internal failure, the odometer display will be blank. Dimming is handled by the potentiometer that controls instrumentation illumination. Also, if there is a CCD bus failure, "no bus" will be displayed on the odometer 20 seconds after the vehicle is started.
Lamps (Hardwired)
The following lamps are hardwired in the cluster and are not part of the self-test.
Full Time 4WD
Seat Belt
ABS (amber)
High Beam
Left Turn Signal
Right Turn Signal
Security (if equipped)
Low Wash
Wait to Start
Lamps (CCD)
The cluster via CCD messages controls the following lamps. They are actuated during the selftest procedure.
ABS lamp
Brake Warning
Low Fuel Warning - Internally Controlled by the
Cluster not CCD
Airbag
Upshift (if equipped)
Check Engine
Check Gauges
Cruise Control Lamp
Trans Temp
O/D OFF (if equipped)
Water in Fuel
Maintenance Required (5.9 Heavy Duty Only)
NOTE: THE SEAT BELT AND LOW WASHER SWITCH AND BRAKE WARNING LAMP ARE HARDWIRED TO THE CLUSTER. THE CLUSTER THEN DECIDES IF THE LAMP SHOULD BE ILLUMINATED.
DIAGNOSTICS
GAUGES
The instrument cluster will not store any DTCs. Because the engine controller PCM gathers all the gauge information and sends it to the cluster via the bus, it is the controller's responsibility to monitor these inputs and store DTCs for them. For this reason the first item to be checked regarding a gauge problem (except oil pressure) should be the engine controller for any DTCs relating to the gauge in question.
There are DTCs associated with all the gauges except for the oil pressure gauge. When diagnosing gauges, the input that is used for the gauge message (fuel level sender for example) must be valid. Because of OBD II requirements, most of the information used for monitoring the OBD II system happens to be the same information used by the controller to formulate the gauge bus messages. OBD II Requirements State that the fuel level sender must be checked for rationality. This includes determining if the sending unit voltage is too high or too low or if the voltage hasn't changed over time. If the PCM has determined that the sender information isn't valid, it will send a diagnostic trouble code. The presence or absence of the fuel level sending code in the PCM is and important factor to determine whether a fuel gauge problem is in the sending unit or the cluster.
The same situation is used in all cluster diagnostics related to gauge operation with the exception of the oil pressure gauge. OBD II requirements do not include oil pressure monitoring. Therefore, oil pressure diagnostics would dictate that a mechanical oil pressure gauge be attached to the engine for absolute verification of oil pressure readings.
Hard Wired Lamps
The cluster contains several hard wired lamps described earlier. These lamps are set up in two configurations. Either the cluster supplies power and ground is supplied by the circuit being monitored or the lamp is supplied ground by the cluster and power comes from a module or other device. Refer to the schematic for the specific details on the lamp in question. Verification of the bulb filament may be required in cases of an inoperative lamp. This will require removal of the cluster and the bulb in question.
NOTE: ALL RED WARNING LAMPS EXCEPT THE WAIT TO START LAMP ARE LIGHT EMITTING DIODES (LED) LED'S ARE NOT REPLACEABLE, IF DEFECTIVE THE INSTRUMENT CLUSTER MUST BE REPLACED.
CCD Controlled Lamps
The cluster contains several CCD controlled lamps as described earlier. These lamps are part of the diagnostic self-test. When entering the self-test mode, operation of these lamps can be observed. If the bulb fails to operate during the self-test and the bulb filament is good, the cluster assembly will need to be replaced.
NOTE: A FLASHING SEAT BELT LAMP INDICATES THAT THE AIRBAG WARNING LAMP IS NOT OPERATING PROPERLY.
Power Door Locks
The [1][2]CTM controls the door lock actuator assemblies to handle locking and unlocking with the keyfob or interior switch. There is also a door lock inhibit feature that prevents power locking of the doors if the ignition is OFF and the key is in the ignition. Automatic or rolling locks are included as a DRB programmable feature. If the vehicle is moving approximately 15 mph and approximately 10 degrees of throttle opening is seen by the PCM, (the PCM will send this info to the CTM via the CCD bus) indicating acceleration, the CTM will cycle the lock actuators.
RKE/VTSS
The highline [1][2]CTM provides for Remote Keyless Entry (RKE). The base CTM is not able to provide these functions. The presence of this option dictates that the vehicle is equipped with a high line CTM. The VTSS system monitors the door jamb switches and ignition switch to detect unauthorized entry into the vehicle. Once the vehicle is "armed", any one of these inputs can cause the VTSS system to be tripped. Once tripped, the horn and lights will pulse for 3 minutes and if an attempt is made to start the engine, it will start and stall. If the trigger condition is still present, the lights will continue to flash and return to the "armed" state. The cause of the last 4 alarm triggers is stored by the CTM and may be retrieved by the DRB. The system may be disarmed by either an unlock command from a valid RKE key fob or by using a key in either door. Both front door key cylinders are equipped with disarm switches. There is also a VTSS led on the overhead console that provides information to the driver about the state of the vehicle theft system.
The RKE system is placed in the programming mode by the DRB. The system will store up to four key fob codes. Through the DRB, programming of one key fob without deleting the others is possible. If the key fob is stole, all the fob codes stored previously may be erased to provide the owner of the vehicle with an extra sense of security.
Speed Sensitive Intermittent Wipers
The Ram truck equipped with a high line [1][2]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 driver, 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 18 seconds. The speed signal is provided to the [1][2]CTM from the PCM over the CCD bus.
Diagnostics
The [1][2]CTM is fully addressable with the DRB II and it is the recommended method for diagnosis. The CTM reports 6 Diagnostic Trouble Codes. All of the inputs to the CTM can be read with the DRB and the outputs can be actuated. If the inputs are OK and the outputs can be cycled with the DRB, the problem is usually the [1][2]Central Timer Module.
[1][2]CENTRAL TIMER MODULE
DIAGNOSTIC TROUBLE CODES
Cylinder Lock Switch Failure
Door lock Switch Failure
Door Unlock Switch Failure
Wiper Park Switch Failure
EEPROM Checksum Failure
Internal ROM Test Failure
COMPASS MINI-TRIP COMPUTER (CMTC)
This system, located in the overhead console, displays information on outside temperature, compass direction and trip information.
Compass/Temperature Display
This display provides one of eight compass readings to indicate the direction the vehicle is facing and the outside temperature. Pressing the US/M button for more than 10 seconds will toggle to the Compass/Compass in Degree Display. This display provides one of eight compass readings to indicate the direction that the vehicle is facing and provides the compass direction in degrees (0 to 359 °) North is 0 °, East is 90 °, South is 180 ° and West is 270 °.
Trip Odometer (ODO)
Shows the distance traveled in miles or km since the last reset.
Average Fuel Economy (AVE ECO)
Shows the average fuel economy in MPG (miles per gallon) or L/1OOKm since the last reset.
Instantaneous Fuel Economy
Shows the instantaneous fuel economy in MPG (miles per gallon) or L/100 Km.
Distance to Empty (DTE)
Shows the estimated distance that can be traveled with the fuel remaining in the tank. This level calculated using the MPG multiplied by the Fuel Tank Level.
Elapsed Time (ET)
Shows the accumulated ignition on time whenever the CMTC is powered up until a reset takes place.
Step Button
Press this button to cycle through all the mini-trip computer displays.
US/M Button
Press this button to convert all vehicle displays from US to Metric and vice versa.
To Reset the Display
Press the Step and US/M buttons simultaneously for at least two seconds and all resettable conditions will be reset. This will occur only if a resettable function (AVG ECO, ECO, ET) is currently being displayed.
Compass Calibration
This is a Fast Auto-Cal compass that manually enters the calibration mode when the US/M and Step buttons are pressed for more than 6 seconds in the Compass/Temperature screen. The 'CAL' will illuminate to indicate the compass is in calibration mode. Drive the vehicle around in all four compass directions, such as driving around a street block several times or driving in 2-3 circles with a slow to medium speed. When the calibration process is completed, the 'CAL' will go OFF and the compass will function normally. The calibration should take place in an area that is leveled and minimum of 50 feet away from metal objects, power lines, buildings and large steel structures.
If the 'CAL' message remains in the display, either there is excessive magnetism near the compass, or the unit is faulty. If the wrong direction is still indicated in the compass display, the area selected for calibration may be too close to a strong magnetic field. If the compass cannot be calibrated, further diagnosis is necessary.
Compass Variance
Compass Variance is the difference between Magnetic North and Geographic North. In some areas of the country, the difference between Magnetic and Geographic North is great enough to cause the compass to give false readings. If this occurs, the compass variance must be set.
To set the variance: Turn the ignition ON and set display to Comp./Temp. Simultaneously press both the US/M and STEP button for 0.1 to 2 seconds. The VAR indicator will light up and the current zone number will be displayed. Press STEP button to select the proper variance zone as shown on the map. After 5 seconds of inactivity, the displayed zone will be automatically set, and normal operation will resume.
VEHICLE COMMUNICATION
The 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 120 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 2000 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. IF THERE IS A PROBLEM, REFER TO THE VEHICLE COMMUNICATIONS.
Bus Failure Messages
Short to Battery - Either or both of the bus wires are shorted to the battery potential.
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 (+) & 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 2000 Ram Trucks.
Bus Bias Level Too Low - Either of both of the bus wires potentials are significantly below their normal 2.5 volts.
Bus Bias Level Too High - Either of both of the bus wires potentials are significantly above there 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 2000 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.
DRB III ERROR MESSAGES AND BLANK SCREEN
Under normal operation, the DRB will display one of only two error messages:
- User-Requested WARM Boot or User-Requested COLD Boot.
If the DRB should display any other error message, record the entire display and call the MDS2 Hotline, or call for information and assistance at 1-800-374-4040. This is a sample of such an error message display:
ver: 2.14
date: 26 Jul93
file: key_tf.cc
date: Jul 26 1993
line: 548
err: Ox1
User-Requested COLD Boot
Press MORE to switch between this display and the application screen.
Press F4 when done noting information.
DRB III Does Not Power UP (Blank Screen)
If the LED's do not light or no sound is emitted at start up, check for loose cable connections or a bad cable. Check the vehicle battery voltage (data link connector cavity 16). A minimum of 11 volts is required to adequately power the DRB.
If all connections are proper between the DRB and the vehicle or other devices, and the vehicle battery is fully charged, an inoperative DRB may be the result of faulty cable or vehicle wiring.
DRB Scan Tool:
Display Is Not Visible
Low temperatures will affect the visibility of the display. Adjust the contrast to compensate for this condition.
WARNINGS
Vehicle Damage Warnings
Before disconnecting any control module, make sure the ignition is OFF. Failure to do so could damage the module.
When testing voltage or continuity at any control module, use the terminal side (not the wire end) of the connector. Do not probe a wire through the insulation; this will damage it and eventually cause it to fail because of corrosion.
Be careful when performing electrical tests so as to prevent accidental shorting of terminals. Such mistakes can damage fuses or components. Also, a second code could be set, making diagnosis of the original problem more difficult.
Road Testing A Complaint Vehicle
Some complaints will require a test drive as part of the repair verification procedure. The purpose of the test drive is to try to duplicate the diagnostic code or symptom condition.
CAUTION: BEFORE ROAD TESTING A VEHICLE, BE SURE THAT ALL COMPONENTS ARE REASSEMBLED. DURING THE TEST DRIVE, DO NOT TRY TO READ THE DRB SCREEN WHILE IN MOTION. DO NOT HANG THE DRB FROM THE REAR VIEW MIRROR OR OPERATE IT YOURSELF. HAVE AN ASSISTANT AVAILABLE TO OPERATE THE DRB.
REQUIRED TOOLS AND EQUIPMENT
DRB III (diagnostic read-out box)
Jumper Wires
Ohmmeter
Voltmeter
GLOSSARY OF ACRONYMS
ACM airbag control module
AECM airbag electronic control module also called ACM
ASDM airbag system diagnostic module also called ACM
CCD Chrysler Collision Detection (vehicle communications bus)
[1][2]CTM [1][2]central timer module
DAB driver airbag
DLC data link connector
IEM also called low line or base central timer module
JB junction block
MIC mechanical instrument cluster
PAB passenger airbag
PCM powertrain control module
PDC powertrain distribution center
RKE remote keyless entry
SQUIB also called initiator (located in rear of airbag module)
VTSS vehicle theft security system