Charging System - Diagnosis Cadillac Eldorado X

DESCRIPTION

The CS144, 140-amp generator is used along with the Instrument Panel Cluster (IPC) and Powertrain Control Module (PCM). CS stands for charging system; 144 denotes the outside diameter (in millimeters) of the generator stator laminations.

The generator and the related charging system circuitry has self-diagnostic capability. A communication process has been incorporated between the IPC, PCM and CS144 generator. When the generator circuit voltage passes outside of programmed limits (10-16 volts), Diagnostic Trouble Codes (DTC) will set. The malfunction may also be indicated by BATTERY VOLTS LOW, BATTERY VOLTS HIGH or SERVICE ENGINE SOON message on the Driver Information Center (DIC).

The voltage regulator is enclosed in a solid mold, mounted inside the generator. A capacitor, mounted in the end frame, protects the rectifier bridge from high voltage and suppresses radio noise.

OPERATION

The voltage regulator controls the field using a Pulse Width Modulated (PWM) signal, measured in duty cycles. A PWM signal continuously cycles on and off. On-time can vary within each cycle.

When the ignition switch is turned to the RUN position, the PCM applies voltage to the regulator before engine is started. The regulator, now in field strobe function, applies a small percentage of the duty cycle to the field windings, which produce a magnetic field. As generator RPM increases, the field strobe function is disabled and normal regulation occurs.

When field current is on, the regulator switches the field current on and off at a fixed frequency of about 400 cycles per second. By varying the overall time on and off, correct average field current for proper system voltage control is achieved. At high speeds, the on-time may be 10 percent. At low speeds with a heavy electrical load, the on-time may be as much as 90 percent.

The PCM monitors the regulator from the "L" terminal of the generator. The regulator will internally ground the "L" terminal when it detects an internal fault.

ADJUSTMENTS

Note. No adjustment or maintenance is required on generator assembly. Regulator voltage is preset and no adjustment is possible. Drive belt tension is controlled by a belt tensioner.

TROUBLE SHOOTING

Note. For information not covered in this article, see the TROUBLE SHOOTING - BASIC PROCEDURES article in the GENERAL INFORMATION section.

ON-VEHICLE TESTING

Note. Generators are serviced by replacement only.

Note. Before making electrical checks, visually inspect all terminals for clean, tight connections. Check generator mounting bolts and drive belt tension. Ensure battery is in good condition prior to testing charging system.

GENERATOR NOISE DIAGNOSIS

Generator noise may be caused by a loose drive pulley, loose mounting bolts, worn or dirty bearings, defective diode, or defective stator. It is normal to hear a high frequency whine or magnetic noise at full output. An output test should be performed to distinguish bearing noise from a magnetic noise. See GENERATOR FUNCTIONAL CHECK .

A shorted bridge diode will reduce output by 1/3 of the rating and will have a growling noise when at high load. Listening to generator with a moderate load (engine cooling fans or headlights on) can also assist in determining if a bearing or magnetic noise is present.

GENERATOR FUNCTIONAL CHECK

1. Ensure battery is in good condition and fully charged. Check connections at battery and generator. Repair as necessary. Turn off all electrical loads. Connect voltmeter to generator output. Run engine at 2500 RPM for 30 seconds. Check voltage output.
2. With engine at normal operating temperature, voltage should be 13-15 volts. With cold engine, voltage should be 14-16 volts. If voltage is not as specified, replace generator. If voltage is as specified, connect inductive ammeter to battery charging cable. Connect carbon pile (VAT 40) across battery.
3. Run engine at 2500 RPM. Adjust carbon pile to obtain maximum output from generator. If value is within 15 amps of rated output, generator is okay. If value is not within 15 amps of rated output, replace generator.

BENCH TESTING

Note. Information not available from manufacturer.

SELF-DIAGNOSTICS

Note. Vehicle is equipped with elaborate self-diagnostics which covers many on-vehicle systems. This article only covers the portion of those systems which relates to charging system diagnosis.

Note. Diagnosis should not be attempted unless all IPC segments illuminate, as it could lead to misdiagnosis. If any segment is inoperative, affected display panel should be replaced.

Entering Self-Diagnostics

1. Turn ignition on. Simultaneously push OFF and WARMER buttons on Climate Control Center (CCC). Continue pushing OFF and WARMER buttons until segment check appears (about 3 seconds) on Instrument Panel Control (IPC). NOTE: Failure of any segment to glow may result in inaccurate test results. Replace any inoperative segment display before proceeding with self-diagnostic process.
2. When segment check appears (all segments glow), system has entered into self-diagnostic mode. Release both buttons. Driver Information Center (DIC) will display diagnostic trouble codes. Diagnostic trouble code level displays PCM codes first, followed by IPC, ACP, SIR and TCS codes (if so prompted).
3. To proceed to desired level, press and release CCC HI (fan up) button for "yes" or LO (fan down) button for "no". Press LO button to go to next test level (i.e., IPC?, ACP?, SIR? or TCS?) or press OFF button to return to next selection in previous test level.
4. At any time during display of diagnostic trouble codes, system will exit self-diagnostic service mode and return to normal vehicle operation if AUTO or DEFOG button on CCC is pressed.

Diagnostic Trouble Codes (DTCs)

Diagnostic Trouble Codes (DTCs) indicate that IPC has detected a malfunction in a circuit or other system. IPC is programmed with routines for internal checks that it follows only when prescribed test conditions exist. When these conditions exist, IPC checks certain circuits or systems for a malfunction. These checks are called failure conditions. When a failure condition is present, a DTC is set. Some DTCs alert the driver through a Driver Information Center (DIC) message. Other DTCs do not trigger a driver warning. DTCs are not stored in the IPC EEPROM and are not retained after battery is disconnected.

Current DTC

When IPC determines that test conditions and failure conditions for a particular DTC are true, it sets that DTC as CURRENT. All DTCs remain CURRENT until the next time IPC finds test conditions are true and failure conditions are false. A few DTCs remain CURRENT until next ignition cycle or until failure conditions are false several times.

History DTC

After a DTC has been set, IPC continues to monitor for test and failure conditions. For most DTCs, if test conditions are true and failure conditions are false, DTC is changed to HISTORY. Some DTCs require test conditions to be true and failure false several times or require an ignition cycle to change from CURRENT to HISTORY. If there are no CURRENT DTCs for 50 ignition cycles, all HISTORY DTCs will be cleared.

Displaying DTCs

Turn ignition on. Press OFF and WARMER buttons of climate control center/panel until all segments of display are on. Driver Information Center (DIC) will display all DTCs set. Each DTC will be displayed along with its status, CURRENT or HISTORY. DTCs will be displayed in following order: PCM, IPC, ACM, SDM, TCS, RSS, PZM, IRC, RFA, CCP, and PHN. See COMMONLY USED ABBREVIATIONS article in GENERAL INFORMATION section.

This article only covers IPC DTCs. For information on other DTCs, see TESTS W/CODES article in ENGINE PERFORMANCE section. Also see BODY CONTROL MODULE article. Pressing FAN DOWN button will bypass DTC display.

Erasing DTCs

IPC CLEAR CODES option can be used to clear stored IPC DTCs. When selected, IPC CLEAR CODES option immediately erases all DTCs stored to that point and DIC displays IPC CODES CLEAR. Once a malfunction has been corrected, clear DTCs so future service is not duplicated.

DIAGNOSTIC TESTS

Note. Diagnostic trouble code tests are written specifically for use with GM Tech I or Tech II scan tools. Generic scan tool can be used but may have limited functions.

DTC DESCRIPTIONS

DTC B1910 indicates an open in generator L-terminal feedback circuit. Diagnose any CURRENT Powertrain Control Module (PCM) DTCs, before further diagnosis. See TESTS W/CODES article in ENGINE PERFORMANCE section.

Diagnostic Procedure

1. Connect scan tool. Turn ignition on. Using scan tool, select IPC, DATA LIST, INPUTS, and ALT L TERMINAL. If scan tool does not display ON, go to next step. If scan tool displays ON, replace IPC.
2. Turn ignition off. Disconnect IPC connector C1. Disconnect generator. Measure resistance in Red wire between IPC connector C1 terminal A9 and generator L-terminal. (Scheme 3) If resistance is greater than 5 ohms, locate and repair open circuit in Red wire. If resistance is less than 5 ohms, go to next step.
3. Reconnect IPC connector C1. Turn ignition on. Measure voltage between generator connector L-terminal (Red wire) and ground. If battery voltage is present, replace generator. If battery voltage is not present, replace IPC.

DTC B1911 indicates a circuit malfunction is preventing generator from charging. This test is only performed when IPC measures engine speed greater than 600 RPM and service diagnostics is not active.

Probe generator L-terminal (Red wire) and check for battery voltage while engine is running. If battery voltage is present, check for an intermittent short or open circuit in Red wire of L-terminal or Grey wire between generator and PCM.

DTC B1981 indicates that IPC is measuring engine speed greater than 1500 RPM and voltage at IPC connector C1 (terminals A1 and B1) is less than 10 volts.

1. Connect scan tool. Turn ignition off. Using scan tool, select DATA LIST and DATA. If battery voltage displayed on scan tool is 10 volts or less, go to next step. If battery voltage displayed on scan tool is not 10 volts or less, replace IPC.
2. Measure voltage between IPC connector C1 terminal A1 (Orange wire) and ground. (Scheme 3) If voltage is 10 volts or less, check Orange wire for open or short circuit. If circuit is okay, replace generator. If voltage is greater than 10 volts, replace IPC.

DTC B1982 indicates IPC measured battery voltage at IPC connector C1 terminals A1 and B1 is greater than 15.5 volts. DTC may be set if vehicle is connected to a battery charger on "fast" or "boost" charge.

1. Connect scan tool. Turn ignition off. Using scan tool, select DATA LIST, DATA. If voltage displayed on scan tool is 16 volts or more, go to next step. If voltage displayed on scan tool is not 16 volts or more, replace IPC.
2. Measure voltage between IPC connector C1, terminal A1 (Orange wire) and ground. (Scheme 3) If voltage is 16 volts or more, replace generator. If voltage is not 16 volts or more, replace IPC.

DTC B1983 is set when voltage measured at IPC connector C1 terminals A1 and B1 is less than 9 volts.

1. Connect scan tool. Turn ignition off. Using scan tool, select DATA LIST, DATA. If battery voltage displayed on scan tool is 9 volts or less, go to next step. If battery voltage displayed on scan tool is greater than 9 volts, replace IPC.
2. Measure voltage between IPC connector C1 terminal A1 (Orange wire) and ground. (Scheme 3) If voltage is 9 volts or less, locate and repair problem in charging system. See GENERATOR & REGULATOR article in ELECTRICAL section. If voltage is greater than 9 volts, replace IPC.

Scheme 3

OVERHAUL

Generators are serviced by replacement only.

Charging System Schematic (Concours, DeVille, Eldorado & Seville). Scheme 4

See also:
• TROUBLE SHOOTING - BASIC PROCEDURES
• COMMONLY USED ABBREVIATIONS
• TESTS W/CODES
• BODY CONTROL MODULE
• GENERATOR FUNCTIONAL CHECK