Charging System - Generators & Regulators: Other Jeep Liberty I

BATTERY TEMPERATURE SENSOR

The Battery Temperature Sensor (BTS) is attached to the battery tray located under the battery.

The generator is belt driven by the engine using a serpentine type drive belt. It is serviced only as a complete assembly. If the generator fails for any reason, the entire assembly must be replaced.

GENERATOR DECOUPLER PULLEY

The generator decoupler is used only with 2.4L engines. The decoupler is used in place of the standard generator drive pulley. (Scheme 12)

Scheme 12

VOLTAGE REGULATOR

The Electronic Regulator (EVR) is not a separate component. It is actually a voltage regulating circuit located within the Power Control Module (PCM). The EVR is not serviced separately. If replacement is necessary, the PCM must be replaced.

The charging system is turned on and off with the ignition switch. The system is on when the engine is running and the ASD relay is energized. When the ASD relay is on, voltage is supplied to the ASD relay sense circuit at the PCM. This voltage is connected through the PCM and supplied to one of the generator field terminals (Gen. Source +) at the back of the generator.

The amount of DC current produced by the generator is controlled by the EVR (field control) circuitry contained within the PCM. This circuitry is connected in series with the second rotor field terminal and ground.

A battery temperature sensor, located in the battery tray housing, is used to sense battery temperature. This temperature data, along with data from monitored line voltage, is used by the PCM to vary the battery charging rate. This is done by cycling the ground path to control the strength of the rotor magnetic field. The PCM then compensates and regulates generator current output accordingly.

All vehicles are equipped with On-Board Diagnostics (OBD). All OBD-sensed systems, including EVR (field control) circuitry, are monitored by the PCM. Each monitored circuit is assigned a Diagnostic Trouble Code (DTC). The PCM will store a DTC in electronic memory for certain failures it detects.

The Check Gauges Lamp (if equipped) monitors: charging system voltage, engine coolant temperature and engine oil pressure. If an extreme condition is indicated, the lamp will be illuminated. This is done as reminder to check the 3 gauges. The signal to activate the lamp is sent via the CCD bus circuits. The lamp is located on the instrument panel.

The BTS is used to determine the battery temperature and control battery charging rate. This temperature data, along with data from monitored line voltage, is used by the PCM to vary the battery charging rate. System voltage will be higher at colder temperatures and is gradually reduced at warmer temperatures. The PCM sends 5 volts to the sensor and is grounded through the sensor return line. As temperature increases, resistance in the sensor decreases and the detection voltage at the PCM increases. The BTS is also used for OBD II diagnostics. Certain faults and OBD II monitors are either enabled or disabled, depending upon BTS input. Most OBD II monitors are disabled below 20°F (-6.7°C). (Scheme 13)

Scheme 13

As the energized rotor begins to rotate within the generator, the spinning magnetic field induces a current into the windings of the stator coil. Once the generator begins producing sufficient current, it also provides the current needed to energize the rotor.

The stator winding connections deliver the induced AC current to 3 positive and 3 negative diodes for rectification. From the diodes, rectified DC current is delivered to the vehicle electrical system through the generator battery terminal.

Although the generators appear the same externally, different generators with different output ratings are used on this vehicle. Be certain that the replacement generator has the same output rating and part number as the original unit. See GENERATOR APPLICATION table for amperage ratings and part numbers.

Noise emitting from the generator may be caused by: worn, loose or defective bearings; a loose or defective drive pulley; incorrect, worn, damaged or misadjusted fan drive belt; loose mounting bolts; a misaligned drive pulley, or a defective stator or diode.

The generator decoupler is used only 2.4L engines. The decoupler is a one-way clutch designed to help reduce belt tension fluctuation, vibration, reduced fatigue loads, improve belt life, reduce hubloads on components, and reduce noise. Dry operation is used (no grease or lubricants). The decoupler is not temperature sensitive and also has a low sensitivity to electrical load. The decoupler is a non-serviceable item and is to be replaced as an assembly.

The amount of DC current produced by the generator is controlled by EVR circuitry contained within the Powertrain Control Module (PCM). This circuitry is connected in series with the generators second rotor field terminal and ground. Voltage is regulated by cycling the ground path to control the strength of the rotor magnetic field. The EVR circuitry monitors system line voltage, Battery (B+) and battery temperature. It then determines a target charging voltage. If sensed battery voltage is 0.5 volt or lower than the target voltage, the PCM grounds the field winding until sensed battery voltage is 0.5 volt above target voltage. A circuit in the PCM cycles the ground side of the generator field up to 100 times per second (100 Hz). It also has the capability to ground the field control wire 100% of the charging rate cannot be monitored (limp-in), a duty cycle of 25% is used by the PCM in order to have some generator output.

BELT TENSION

Vehicle is equipped with an automatic belt tensioner. Belt tensioner is not adjustable.

PROGRAMMING POWERTRAIN CONTROL MODULE

Note. Before replacing the PCM for a failed driver, control circuit, or ground circuit, be sure to check the related component/circuit integrity for failures not detected due to a double fault in the circuit. Most PCM driver/control circuit failures are caused by internal component failures (i.e.; relays and solenoids) and shorted circuits (i.e.; pull-ups, drivers, and switched circuits). These failures are difficult to detect when a double fault has occurred and only one DTC has been set.

When a PCM (JTEC) and the SKIM are replaced at the same time, perform the following steps in order

1. Program the new PCM (JTEC).
2. Program the new SKIM.
3. Replace all ignition keys and program them to the new SKIM.

Programming PCM (JTEC)

The SKIS Secret Key is an ID code that is unique to each SKIM. This code is programmed and stored in the SKIM, the PCM, and the ignition key transponder chip(s). When replacing the PCM, it is necessary to program the secret key into the new PCM using the DRBIII(R) scan tool. Perform the following steps to program the secret key into the PCM.

1. Turn the ignition switch to the ON position (transmission in Park/Neutral).
2. Use the DRBIII(R) and select THEFT ALARM, SKIM then MISCELLANEOUS.
3. Select PCM REPLACED (GAS ENGINE).
4. Enter secured acess mode by entering the vehicle 4-digit pin.
5. Select ENTER to update PCM VIN.
6. Press ENTER to transfer the secret key (the SKIM will send the secret key to the PCM).
7. Press PAGE BACK to get to the Select System menu and select ENGINE, MISCELLANEOUS, and SRI MEMORY CHECK.
8. The DRBIII(R) will ask, "Is odometer reading between XX and XX?" Select the YES or NO button on the DRBIII(R). If NO is selected, the DRBIII(R) will read, "Enter Odometer Reading (From I.P. odometer)". Enter the odometer reading from the instrument cluster and press ENTER.

Programming The Skim

1. Turn the ignition switch to the ON position (transmission in Park/Neutral).
2. Use the DRBIII(R) and select THEFT ALARM, SKIM, then MISCELLANEOUS.
3. Select PCM REPLACED (GAS ENGINE).
4. Program the vehicle 4-digit PIN into SKIM.
5. Select COUNTRY CODE and enter the correct country.
6. Select YES to update VIN (the SKIM will learn the VIN from the PCM).
7. Press ENTER to transfer the secret key (the PCM will send the secret key to the SKIM).
8. Program ignition keys to the SKIM.

Programming Ignition Keys To The SKIM

1. Turn the ignition switch to the ON position (transmission in Park/Neutral).
2. Use the DRBIII(R) and select THEFT ALARM, SKIM, then MISCELLANEOUS.
3. Select PROGRAM IGNITION KEYS.
4. Enter secured access mode by entering the vehilce 4-digit PIN.
5. Obtain ignition keys to be programmed from the customer (8 keys maximum).
6. Using the DRBIII(R), erase all ignition keys by selecting MISCELLANEOUS, and ERASE ALL CURRENT IGN. KEYS.
7. Program all of the ignition keys. If ignition key programming is unsuccessful, the DRBIII(R) will display one of the following messages: Programming Not Attempted The DRBIII(R) attempts to read the programmed key status and there are no keys programmed into SKIM memory. Programming Key Failed (Possible Used Key From Wrong Vehicle) SKIM is unable to program an ignition key transponder due to one of the following: The ignition key transponder is faulty. The ignition key transponder is or has been already programmed to another vehicle. 8 Keys Already Learned, Programming Not Done The SKIM transponder ID memory is full. Learned Key In Ignition The ID for the ignition key transponder currently in the ignition lock cylinder is already programmed in SKIM memory.

INITIAL CHECKS

Before proceeding with charging system diagnosis, ensure following conditions are met

1. Battery is fully charged and in good condition.
2. Battery cables are in good condition with connections clean and secure.
3. Generator belt is in good condition and properly tightened. See «BELT TENSION»(ref-164631-S14416555462004081100000) under ADJUSTMENTS.
4. Generator and PCM wiring harness connections are clean and tight.
5. Engine ground strap is in place.

1. The check gauges lamp (if equipped) is illuminated with the engine running.
2. The voltmeter (if equipped) does not register properly.
3. An undercharged or overcharged battery is often caused by: Accessories being left on with the engine not running. A faulty or improperly adjusted switch that allows a lamp to stay on.

GENERATOR DECOUPLER

If there is noise coming from the decoupler, or if it does not drive the generator (generator not charging), there is an internal failure. Replace decoupler.

SERVICE PRECAUTIONS

Before proceeding with diagnosis, observe following precautions

1. Ensure battery is fully charged.
2. Probe PCM connector from pin side. DO NOT backprobe PCM connector or probe wires through insulation.
3. DO NOT cause short circuits when performing electrical tests. This will set additional DTCs, making diagnosis of original problem more difficult.
4. DO NOT use a test light in place of a voltmeter.
5. Always begin repair with lowest DTC number (MIL) or first DTC displayed (scan tool).
6. Always perform appropriate verification (VER) test after repairs are made.
7. Always disconnect scan tool after use.
8. Always disconnect scan tool before charging battery.

Note. PCM cannot diagnose every charging system problem. If fault still exists after performing self-diagnostic procedures, proceed to ON-VEHICLE TESTING .

Blank Message Screen

Check for loose cable connections or bad cable. If cable connections and cable are okay, check voltage at DLC terminal No. 16 (Pink/Red wire). Voltage should be at least 11 volts. If voltage is not as specified, check wiring circuit and necessary fuses. See WIRING DIAGRAMS .

Possible Causes

1. Battery Temp Volts Below 0.0392 Volt
2. Battery Temperature Sensor
3. (K118) Batt Temp Signal Circuit Shorted To Ground
4. (K118) Batt Temp Signal Circuit Shorted To The (K4) Sensor Ground Circuit
5. PCM

1. Battery Temp Sensor Voltage Above 4.9412 Volts
2. Battery Temperature Sensor
3. (K118) Batt Temp Signal Circuit Shorted To Battery Voltage
4. (K118) Batt Temp Signal Circuit Open
5. (K4) Sensor Ground Circuit Open
6. PCM

1. Good Trip Equal To Zero
2. Battery Positive Circuit High Resistance
3. Generator Ground High Resistance
4. Generator Operation
5. (K20) Gen Field Control Circuit Open
6. (K20) Gen Field Control Circuit Shorted To Ground
7. (Z142) Ground Circuit Open
8. PCM

1. Good Trip Equal To Zero
2. Generator Operation
3. (K20) Gen Field Control Circuit Shorted To Battery Voltage
4. PCM

1. Good Trip Equal To Zero
2. Battery Positive Circuit High Resistance
3. Case Ground High Resistance
4. Generator Operation
5. (Z142) Gen Ground Circuit Open
6. (K20) Gen Field Control Circuit Shorted To Battery Voltage
7. (K20) Gen Field Control Circuit Open
8. (K20) Gen Field Control Circuit Shorted To Ground
9. PCM

INTERMITTENT CONDITION

Note. The conditions that set the DTC are not present at this time. The following list may help in identifying the intermittent condition.

1. Refer to any TSB's that apply.
2. Review the DRB Freeze Frame information. If possible, try to duplicate the conditions under which the DTC was set.
3. With the engine running at normal operating temperature, monitor the DRBIII(R) parameters related to the DTC while wiggling the related wire harness. Look for parameter values to change and/or a DTC to set.
4. Turn the ignition off.
5. Visually inspect the related wire harness. Disconnect all the related harness connectors. Look for any chafed, pierced, pinched, partially broken wires and broken, bent, pushed out, or corroded terminals.
6. Perform a voltage drop test on the related circuits between the suspected faulty component and the PCM. See «VOLTAGE DROP TEST»(ref-164631-S04144341302004081100000) .
7. Inspect and clean all PCM, engine, and chassis grounds that are related to the most current DTC.
8. If numerous trouble codes were set, use a wire schematic and look for any common ground or supply circuits.
9. For any related DTC's, actuate the Relay with the DRBIII(R) and wiggle the related wire harness to try to interrupt the actuation.
10. Use the DRBIII(R) to perform a SYSTEM TEST if one applies to failing component.
11. A co-pilot, data recorder, and/or lab scope should be used to help diagnose intermittent conditions.
12. If any problems were found during the above inspections, repair as necessary. See «POWERTRAIN VERIFICATION TEST VER-5»(ref-164631-S16173665432004081200000) under VERIFICATION TESTS. If no problems were found test is complete.

Note. The battery temperature sensor is located under the vehicle battery and is attached to a mounting hole on battery tray. (Scheme 14)

Scheme 14

The generator decoupler is used only with 2.4L engines. Two different type generator decoupler pulleys are used. One can be identified by the use of machined splines. (Scheme 15) The other can be identified by a hex opening and will not use splines. (Scheme 16) Different special tools are required to service each different decoupler.

Scheme 15

Scheme 16