Battery: Diagnosis Chevrolet TrailBlazer I

Diagnostic Starting Point - Engine Electrical

Begin the system diagnosis with the DIAGNOSTIC SYSTEM CHECK - ENGINE ELECTRICAL . The Diagnostic System Check will provide the following information

1. The identification of the control module(s) which command the system.
2. The ability of the control module(s) to communicate through the serial data circuit.
3. The identification of any stored diagnostic trouble codes (DTCs) and their status.

The use of the Diagnostic System Check will identify the correct procedure for diagnosing the system and where the procedure is located.

Circuit Description

The PCM monitors the system voltage to make sure that the voltage stays within the proper range. If the PCM detects an excessively low system voltage, DTC P0562 will set.

When the charging system detects a fault, the instrument panel cluster (IPC) displays a message or the charge indicator will light.

Conditions for Running the DTC

1. Engine run time more than 20 seconds and above 1200 RPM.
2. Vehicle speed above 8 km/h (5 mph).

Conditions for Setting the DTC

The PCM detects an improper voltage below 11 volts for 5 seconds.

Action Taken When the DTC Sets

1. The PCM stores the DTC information into memory when the diagnostic runs and fails.
2. The PCM will store conditions which were present when the DTC set as Failure Records data only.
3. The PCM disables most outputs.
4. The transmission defaults to a predetermined gear.
5. The torque converter clutch (TCC) operation is inhibited.
6. The instrument panel cluster (IPC) displays a message.
7. The malfunction indicator lamp (MIL) will not illuminate.

Conditions for Clearing the DTC

1. The Conditions for Setting the DTC are no longer present.
2. A history DTC will clear after 40 malfunction free ignition cycles.
3. The powertrain control module (PCM) receives the clear code command from the scan tool.

Scheme 20

The powertrain control module (PCM) continuously monitors that the system voltage stays within the proper range. If the PCM detects an excessively high system voltage, DTC P0563 will set. A high voltage condition may cause a stalling condition or other driveability concerns.

1. The engine run time is more than 20 seconds.
2. Engine running above 1200 RPM.
3. Vehicle speed above 8 km/h (5 mph).

1. The PCM senses the system voltage is above 19 volts.
2. All of the conditions are present for 5 seconds.

1. The PCM stores DTC P0563 in the PCM memory when the diagnostic runs and fails.
2. The PCM will record the operating conditions at the time the diagnostic fails. The PCM stores this information in Failure Records.
3. The PCM disables most outputs.
4. The transmission defaults to a predetermined gear.
5. The torque converter clutch (TCC) operation is inhibited.
6. The instrument panel cluster (IPC) displays a message.
7. The malfunction indicator lamp (MIL) will not illuminate.

1. The Conditions for Setting the DTC are no longer present.
2. A history DTC will clear after 40 malfunction free ignition cycles.
3. The Powertrain Control Module (PCM) receives the clear code command from the scan tool.

Scheme 21

The PCM uses the generator turn on signal circuit to control the load of the generator on the engine. A high side driver in the PCM applies a voltage to the voltage regulator. This signals the voltage regulator to turn the field circuit ON and OFF. When the PCM turns ON the high side driver, the voltage regulator turns ON the field circuit. When the PCM turns OFF the high side driver, the voltage regulator turns OFF the field circuit.

The PCM monitors the state of the generator turn on signal circuit. The PCM should detect a low generator turn on signal circuit voltage when the key is ON and the engine is OFF, or when the charging system malfunctions. With the engine running, the PCM should detect a high generator turn on signal circuit. The PCM performs key ON and RUN tests to determine the status of the generator turn on signal circuit. During the key ON test, if the PCM detects a high generator turn on signal circuit voltage, DTC P0621 will set. DTC P0621 will also set if, during the RUN test, the PCM detects a low generator turn on signal circuit. When the DTC sets, the PCM will send a class 2 serial data message to the IPC to illuminate the charge indicator.

1. The ignition is ON.
2. The engine speed is more than 1000 RPM.

1. The PCM detects the GEN L-Terminal active with the ignition ON.
2. The PCM detects the GEN L-Terminal inactive with the engine operating.
3. The above conditions are present for 6 seconds.

1. The PCM will record the operating conditions presents when the DTC set as Failure Records data only.
2. The instrument panel cluster (IPC) displays a message.
3. The malfunction indicator lamp (MIL) will not illuminate.

1. The Conditions for Setting the DTC are no longer present.
2. A history DTC will clear after 40 malfunction free ignition cycles.
3. The Powertrain Control Module (PCM) receives the clear code command from the scan tool.

Scheme 22

The PCM uses the generator field duty cycle signal circuit to monitor the duty cycle of the generator. The generator field duty cycle signal circuit connects to the high side of the field winding in the generator. A pulse width modulated (PWM) high side driver in the voltage regulator turns the field winding ON and OFF. The PCM uses the PWM signal input to determine the generator load on the engine. This allows the PCM to adjust the idle speed to compensate for high electrical loads.

The PCM monitors the state of the generator field duty cycle signal circuit. When the key is in the RUN position and the engine is OFF, the PCM should detect a duty cycle near 0 percent. However, when the engine is running, the duty cycle should be between 5 percent and 100 percent. The PCM monitors the PWM signal using a key ON test and a RUN test. During the tests, if the PCM detects an out of range PWM signal, DTC P0622 will set. When the DTC sets, the PCM will send a class 2 serial data message to the IPC to illuminate the charge indicator.

Key ON Test

1. No generator, CKP sensors, or CMP sensor DTCs are set.
2. The key is in the RUN position.
3. The engine is not running.

Run Test

1. No generator, CKP sensors, or CMP sensor DTCs are set.
2. The engine is less than 3000 RPM.

1. During the ignition ON test, the PCM detects a PWM signal is out of range.
2. During the RUN test, the PCM detects a PWM signal less then 5 percent for more than 6 seconds.

1. The PCM will store the conditions present when the DTC set as Fail Records data only.
2. The malfunction indicator lamp (MIL) will not illuminate.

1. The Conditions for Setting the DTC are no longer present.
2. A history DTC will clear after 40 malfunction free ignition cycles.
3. The Powertrain Control Module (PCM) receives the clear code command from the scan tool.

Scheme 23

The powertrain control module (PCM) uses the generator turn ON signal circuit to control the generator. A high side driver within the PCM allows the PCM to turn the generator ON and OFF. When generator operation is desired, the PCM sends a 5 volt signal to the voltage regulator via the generator turn ON signal circuit. This causes the voltage regulator to begin controlling the generator field circuit. Once the generator is enabled by the PCM, the voltage regulator controls generator output independently of the PCM. Under certain operating conditions, the PCM can turn OFF the generator by turning OFF the 5 volt signal on the generator turn ON signal circuit. The PCM has fault detection circuitry which monitors the state of the generator turn ON signal circuit. If the fault detection circuit senses a voltage other than what is expected, this DTC will set. The voltage regulator also contains fault detection circuitry. If the regulator detects a problem, the regulator will ground the generator turn on signal circuit, pulling the voltage low. This also causes the PCM to set the DTC.

1. The ignition is ON.
2. System voltage between 9.0-18.0 volts.

1. An improper voltage level has been detected on the generator L-terminal circuit.
2. The above conditions are present for at least 30 seconds.

The PCM stores conditions which were present when the DTC set as Failure Records only. This information will not be stored as Freeze Frame Records.

Conditions for Clearing the MIL/DTC

1. The DTC becomes history when the conditions for setting the DTC are no longer present.
2. The history DTC clears after 40 malfunction free warm-up cycles.
3. The PCM receives a clear code command from the scan tool.

Scheme 24

The PCM uses the generator field duty cycle signal circuit to monitor the duty cycle of the generator. The generator field duty cycle signal circuit connects to the high side of the field winding in the generator. A pulse width modulated (PWM) high side driver in the voltage regulator turns the field winding ON and OFF. The PCM uses the PWM signal input to determine the generator load on the engine. This allows the PCM to adjust the idle speed to compensate for high electrical loads.

The PCM monitors the state of the generator field duty cycle signal circuit. When the key is in the RUN position and the engine is OFF, the PCM should detect a duty cycle near 0 percent. However, when the engine is running, the duty cycle should be between 5 percent and 100 percent. The PCM monitors the PWM signal using a key ON test and a RUN test. During the tests, if the PCM detects an out of range PWM signal, DTC P1638 will set. When the DTC sets, the PCM will send a class 2 serial data message to the IPC to illuminate the charge indicator.

1. No generator, CKP sensors, or CMP sensor DTCs are set.
2. The key is in the RUN position.
3. The engine is not running.

1. No generator, CKP sensors, or CMP sensor DTCs are set.
2. The engine is less than 3000 RPM.

1. During the ignition ON test, the PCM detects a PWM signal is out of range.
2. During the RUN test, the PCM detects a PWM signal less then 5 percent for more than 6 seconds.

1. A last test failed, or current DTC, clears when the diagnostic runs and does not fail.
2. A history DTC will clear after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
3. Use a scan tool in order to clear the DTC.

Diagnostic Aids

1. DTCs P1637 and P1638 may set at the same time depending on the failure.
2. Use a scan tool in order to diagnosis the generator circuits. The scan tool should display Inactive for the L terminal and 10-40 percent for the F terminal when the ignition is ON. When the engine is operating, the display should indicate that the L terminal is Active and the F terminal is more than 10 percent.
3. A generator fault, such as a shorted output diode, malfunctioning regulator, open or shorted rotor, or open sense lead or battery feed may cause a low battery charge. Refer to «CHARGING SYSTEM TEST»(ref-188502-S28211951432005090500000) for further information and generator diagnosis.

Scheme 25

Scheme 26

Symptoms - Engine Electrical

1. Perform «DIAGNOSTIC SYSTEM CHECK - ENGINE ELECTRICAL»(ref-188502-S41224358172005090500000) before using the Symptom Tables in order to verify that all of the following are true: There are no DTCs set. The control module(s) can communicate via the serial data link.
2. Review the system operation in order to familiarize yourself with the system functions. Refer to one of the following system operations: «BATTERY DESCRIPTION AND OPERATION»(ref-188502-S34026793752005090500000) «CHARGING SYSTEM DESCRIPTION AND OPERATION»(ref-188502-S30220205652005090500000)

Visual/Physical Inspection

1. Inspect for aftermarket devices which could affect the operation of the Starting and Charging Systems. Refer to CHECKING AFTERMARKET ACCESSORIES in Wiring Systems.
2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

1. «BATTERY INSPECTION/TEST»(ref-188502-S42292285732005090500000)
2. «CHARGE INDICATOR ALWAYS ON»(ref-188502-S41700856652005090500000)
3. «CHARGE INDICATOR INOPERATIVE»(ref-188502-S39351345962005090500000)
4. «CHARGING SYSTEM TEST»(ref-188502-S28211951432005090500000)

Follow these instructions in order to avoid an incorrect diagnosis because of connections

1. If testing the vehicle with the battery cables still connected, wiggle the J 42000 clips on the terminal bolt. This may cut through any coating or through any oxidation that may be present on the bolt. Even new bolts contain a protective coating that may insulate or cause a resistance in the test circuit.
2. If correct connections to the battery terminal bolts in the vehicle are in doubt, perform the following steps: Disconnect the negative battery cable. Disconnect the positive battery cable. Install the test adapters on the terminals. Follow the instructions for testing a removed battery.
3. If the tester displays a REPLACE BATTERY or BAD CELL-REPLACE result for a battery tested in the vehicle with the battery cables connected, perform the following steps: Disconnect the negative battery cable. Disconnect the positive battery cable. Install the tester adapters. IMPORTANT: Always write the test code displayed by the tester on the repair order for any warranty purposes. The number is a unique code that describes the test data for a particular battery at a particular time. The test code may occasionally repeat when you retest the same battery. More often, each test will result in a different code. Use the test code from the second, or Out of Vehicle test. Follow the instructions for testing a removed battery. Replace the battery only if the second test shows a REPLACE BATTERY or BAD CELL-REPLACE result. Use the test code from the second test for any warranty purposes.
4. Use the correct terminal adapters. Do not use any common bolts or a combination of bolts, of nuts, and of washers as adapters when testing the battery. Use the test adapters that are provided with the J 42000 or GM P/N 12303040 terminal adapters. If the adapters that are provided with the J 42000 require replacement, use GM P/N 12303040. Any other adapter may not contact the correct areas of the battery terminal, causing a resistance that may result in an invalid battery test result.

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Tools Required

J 42000 Battery Tester

1. For best results, use an automatic taper-rate battery charger with a voltage capability of 16 volts.
2. The charging area should be well ventilated.
3. Do not charge a battery that appears to be frozen; allow the battery to warm to room temperature and test it using the J 42000 before charging.