Pinpoint Test B: System Voltage Low Or Battery Is Discharged
Pinpoint Test
Pinpoint Test B: System Voltage Low or Battery is Discharged
Refer to Wiring Diagram Set 12, Charging System for schematic and connector information Electrical Diagrams.
Normal Operation
With the engine running, the charging system supplies voltage to the battery and the vehicle electrical system through the battery B+ cable. The voltage that is supplied to the vehicle electrical system operates the various vehicle systems and modules. Many modules monitor this voltage and set a DTC if the voltage drops below their calibrated setpoint.
- DTC P1794:16 (Battery Voltage Circuit: Circuit Voltage Below Threshold)- Sets when the module senses battery voltage is less than 9 volts.
- DTC P065B:09 (Generator Control Circuit Range/Performance: Component Failure)- Sets when the generator reports an internal regulator failure.
- DTC U3003:16 (Battery Voltage: Circuit Voltage Below Threshold)- Sets when the module senses battery voltage is less than 9 volts.
This pinpoint test is intended to diagnose the following:
- High-current fuse assembly
- Abnormal ignition-off current drain(s)
- Engine, generator and battery grounds
- Positive battery cable
- Wiring, terminals or connectors
- Battery
- Generator
- PCM
PINPOINT TEST B : SYSTEM VOLTAGE LOW OR BATTERY IS DISCHARGED
NOTE: Make sure battery voltage is greater than 12.2 volts prior to and during this pinpoint test.
NOTE: Do not have a battery charger attached during vehicle testing.
B1 CHECK THE PCM DTCs
- Ignition ON.
- Enter the following diagnostic mode on the scan tool: Self-Test- PCM.
- Check the PCM for DTCs.
Is DTC P065B:09 present?
Yes
INSTALL a new generator. REFER to Generator Service and Repair. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
No
GO to B2.
B2 CHECK BATTERY CONDITION
- and carry out Pinpoint Test A: Battery Condition Test to determine if the battery can hold a charge and is OK for use Pinpoint Tests.
Does the battery pass the condition test?
Yes
GO to B3.
No
INSTALL a new battery. TEST the system for normal operation.
B3 CHECK THE GENERATOR CONNECTIONS
- Ignition OFF.
- Inspect generator C102A connection. Connector should be installed correctly and tight.
- Inspect generator C102A for bent and/or pushed-out pins.
- Inspect generator C102B, B+ circuit SBF01 (RD) connection. The connection should be tight.
- Measure the battery voltage.
- Measure the voltage between generator C102B, B+ circuit SBF01 (RD) and ground.
Is the generator C102B connection tight and does the generator B+ measure battery voltage within ±0.5 volt?
Yes
GO to B4.
No
TIGHTEN or INSTALL a new C102B (B+ nut) or REPAIR connection as needed. REFER to Specifications. VERIFY the high current fuse assembly is OK. If the fuse assembly is OK, REPAIR circuit SBF01 (RD). If the fuse assembly is not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short Electrical Diagrams. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
B4 CHECK THE VOLTAGE DROP IN THE B+ CIRCUIT
- Start the engine.
- With the engine running at idle, headlamps on and blower on high, measure the voltage drop between generator B+ C102B, circuit SBF01 (RD) and the positive battery terminal.
- Carry out a wiggle test of the generator wiring and connections while measuring voltage drop.
Is the voltage drop less than 0.5 volt?
Yes
GO to B5.
No
INSPECT and REPAIR any corrosion in the B+ circuit SBF01 (RD) or positive battery cable connections. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
B5 CHECK THE VEHICLE GROUNDS
- Start the engine.
- With the engine running at idle, headlamps on and heater blower on high, measure the voltage drop between the generator housing and the negative battery terminal.
Is the voltage drop less than 0.5 volt?
Yes
GO to B6.
No
INSPECT and REPAIR the engine ground, generator ground or the battery ground for corrosion. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
B6 COMPARE PCM SUPPLY VOLTAGE (VPWR) PID
- Enter the following diagnostic mode on the scan tool: PCM DataLogger.
- Monitor PCM VPWR PID.
- With the engine still running at idle, headlamps on and blower on high, measure the battery voltage at the battery and monitor the PCM VPWR PID.
Does PCM VPWR PID display battery voltage within ±0.5 volt?
Yes
GO to B7.
No
REPAIR high resistance or loose connections in the affected PCM power circuit(s). CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
B7 CHECK PCM GROUND FOR HIGH RESISTANCE
- Monitor PCM VPWR PID.
- With the engine still running at idle, turn off all accessory loads, measure the battery voltage at the battery and note the PCM VPWR PID.
- With the engine still running at idle, turn headlamps on and blower on high, measure the battery voltage at the battery and monitor the PCM VPWR PID.
Does the VPWR PID read within ±0.5 volt with accessory loads on as compared to accessory loads off?
Yes
GO to B8.
No
REPAIR the affected PCM ground circuits. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
B8 MONITOR PID VPWR AT WOT (Wide Open Throttle)
- With the engine still running at idle, turn off all accessory loads, measure the battery voltage at the battery and monitor the PCM VPWR PID.
- Monitor the VPWR PID and momentarily accelerate the engine to WOT (Wide Open Throttle) and release. Repeat this step 4-5 times while continuing to monitor the VPWR PID.
Does the VPWR PID stay within 0.5 volt of battery voltage when the engine rpms are increased?
Yes
CARRY OUT the Component Test, Battery - Drain Test Component Tests and General Diagnostics. REFER to Battery.
No
INSTALL a new PCM. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.