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HOMESERVICE MANUALSPONTIAC2008GRAND PRIX BASEREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 99 (BATTERY, CHARGING SYSTEM AND STARTING SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESCHARGING SYSTEM TEST
2008 Pontiac Grand Prix Base

Charging System Test

2008 Pontiac Grand Prix BaseSECTION Charging System Test
WARNING: This page is about a different car, the 2007 Buick LaCrosse and 2007 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.
Charging System Test

Step Action Value(s) Yes No
1 Did you perform the Diagnostic System Check - Vehicle? - Go to Step 2  Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2 With ignition OFF, install the Midtronics Digital Battery Analyzer and verify the condition of the battery.
Is the battery sufficiently charged for testing?		 - Go to Step 3  Go to Battery Inspection/Test 
3
  1. Disconnect the Midtronics Digital Battery Analyzer.
  2. Connect the Sun Vat 40 tester or equivalent to the battery.
  3. Turn the ignition to the OFF/LOCK position.
  4. Observe and record the battery voltage reading at the battery terminals on the Sun Vat 40 tester.
  5. Start the engine and observe the system voltage reading on the tester.
Does the voltage increase from the first specified (engine OFF) to the second (engine ON specified range).		 Engine Off = B+ Engine On = 13.9 - 15.5 V Go to Step 4  Go to Step 6 
4
  1. Turn on the following accessories:
    • Headlights - HI beams
    • A/C on Max
    • Blower Fan - On high
    • Rear window defogger
    • Heated seats (If equipped)
  2. Maintain engine speed at 2,500 RPM.
Is voltage still within the specified value?		 13.9 - 15.5 V Go to Step 5  Go to Step 6 
5
  1. Turn OFF all accessories.
  2. Turn OFF the ignition.
  3. Connect a carbon pile tester to the vehicle.
    4. IMPORTANT: When measuring generator output current, be sure the inductive probe encircles the generator output wire.
  4. Connect an inductive ammeter probe to the output circuit of the generator.
  5. Start the engine.
  6. Increase engine speed to 2,500 RPM.
  7. Adjust the carbon pile as necessary in order to obtain the maximum current output.
Is the generator output greater than or equal to the load test value as specified in Generator Usage  ?		 - System OK Go to Step 10 
6
  1. Turn the engine OFF.
  2. Disconnect the generator harness connector.
  3. Turn the ignition to the ON position.
  4. Using a DMM, measure the voltage on the L terminal circuit.
Is the voltage greater than the specified value?		 L26 = 0V
LY7 = 1.2V		 Go to Step 11  Go to Step 7 
7
  1. Turn the engine OFF.
  2. Start the engine and check the voltage on the L terminal.
Is the voltage within the specified value?		 L26 = 5V
LY7 = 9.5V		 Go to Step 8  Go to Step 12 
8
  1. Turn engine OFF.
  2. Turn ignition switch to ON position.
  3. Using the scan tool, observe the duty cycle in the F-terminal signal parameter.
Does the scan tool display the indicated value?		 0% Go to Step 9  Go to Step 13 
9 Connect a test lamp to B+ and repeatedly touch the F-terminal at the generator harness connector while monitoring the GEN-F terminal signal parameter on the scan tool.
Does the scan tool indicate that the generator pulse width modulation (PWM) is above the specified range?		 90% Go to Step 10  Go to Step 14 
10
  1. Turn the engine OFF.
  2. Inspect the generator B+ output terminal at the generator for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 19  Go to Step 15 
11 Test the L terminal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 19  Go to Step 16 
12 Test the L terminal circuit for open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 19  Go to Step 16 
13 Test the GEN-F terminal for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 19  Go to Step 16 
14 Test the GEN-F terminal circuit for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 19  Go to Step 16 
15 Inspect for poor connections at the generator. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 19  Go to Step 18 
16 Inspect for poor connections at the harness connector of the powertrain control module (PCM) / engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 19  Go to Step 17 
17
IMPORTANT: The replacement PCM/ECM must be programmed.
Replace the PCM/ECM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.Did you complete the replacement?		 - Go to Step 19  -
18 Replace the generator. Refer to Generator Replacement (L26)  or Generator Replacement (LY7) .
Did you complete the replacement?		 - Go to Step 19  -
19 Operate the vehicle in order to verify the repair.
Did you correct the condition?		 - System OK Go to Step 2 
RENDER: 1.0x

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Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.