Encountering a situation where your OBD2 scanner fails to communicate with your 1999 Pontiac Bonneville can be frustrating, especially when you need to diagnose a Check Engine Light or prepare for a vehicle inspection. A non-communicating OBD2 port means you’re unable to retrieve crucial diagnostic trouble codes (DTCs), hindering your ability to understand and resolve potential car issues. Before assuming a major electrical problem, know that often, the fix can be surprisingly simple. This guide will walk you through the initial troubleshooting steps to get your OBD2 port communicating again, specifically for your 1999 Pontiac Bonneville.
Common Causes of OBD2 Communication Failure in a 1999 Pontiac Bonneville
Several factors can lead to a 1999 Pontiac Bonneville OBD2 port not communicating. Let’s explore the most common and easiest-to-check culprits first:
Blown Fuse: The Cigarette Lighter Connection
Often, a seemingly unrelated system can impact your OBD2 port’s functionality. In many vehicles, including the 1999 Pontiac Bonneville, the OBD2 port circuit is sometimes linked to the cigarette lighter fuse. A blown fuse in this circuit can cut power to the OBD2 port, rendering it unable to communicate with a scan tool.
Solution:
- Locate your fuse box: Refer to your 1999 Pontiac Bonneville owner’s manual for the location of the fuse box, typically found under the dashboard or in the engine compartment.
- Identify the cigarette lighter fuse: Consult the fuse box diagram (usually printed on the fuse box cover or in your owner’s manual) to pinpoint the fuse for the cigarette lighter (sometimes labeled as “Cigar,” “Aux Power,” or similar).
- Inspect the fuse: Carefully remove the fuse using a fuse puller (often found in the fuse box). Examine the fuse – if the thin wire inside is broken or melted, the fuse is blown and needs replacement.
- Replace the fuse: Replace the blown fuse with a new fuse of the exact same amperage rating. Using a fuse with a higher amperage can damage your vehicle’s electrical system.
Image: A generic fuse box diagram showing fuse locations and labels, similar to what you might find in a 1999 Pontiac Bonneville owner’s manual.
After replacing the fuse, try connecting your OBD2 scanner again to see if communication is restored.
Verifying Power and Ground at the OBD2 Port
If the fuse isn’t the issue, the next step is to check for power and ground directly at the OBD2 port. The OBD2 port requires both power and ground to operate correctly.
How to Check Power and Ground:
- Gather your tools: You’ll need a multimeter and your 1999 Pontiac Bonneville key in the “ON” position (engine not necessarily running).
- Locate pins 4, 16, and 5 (optional) on the OBD2 port:
Image: OBD2 port pinout diagram showing pin 4 as ground and pin 16 as battery voltage, crucial for powering scan tools.
- Pin 16: Provides battery voltage (12V power).
- Pin 4: Chassis ground.
- Pin 5: Signal ground (less critical for powering the scan tool, but good to check).
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Test for Power:
- Set your multimeter to measure DC Voltage.
- Connect the black probe of your multimeter to a known good ground (like a clean, unpainted metal part of the car chassis).
- Touch the red probe to Pin 16 of the OBD2 port.
- You should read approximately 12 volts (battery voltage). If you get no reading, there’s a power supply issue to the OBD2 port.
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Test for Ground:
- Keep your multimeter set to DC Voltage.
- Connect the red probe of your multimeter to the positive battery terminal or Pin 16 (where you confirmed power).
- Touch the black probe to Pin 4 of the OBD2 port.
- You should read approximately 12 volts (or battery voltage). Alternatively, switch your multimeter to continuity mode and check for continuity between Pin 4 and a known good ground. You should hear a beep or see a near-zero resistance reading indicating a good ground.
- Optionally, repeat the ground test for Pin 5 as well.
If you’re missing power or ground, you’ll need to trace the wiring to identify breaks, shorts, or further fuse issues in the circuit. Consult a wiring diagram for your 1999 Pontiac Bonneville to assist in tracing the OBD2 port wiring.
Could it Be Technician Error?
In rare cases, a “no communication” issue might not be with your car at all, but rather with the scan tool or the technician using it. It’s possible, though less likely, that:
- Scan tool malfunction: The scan tool itself could be faulty. Try using a different scan tool if available.
- Improper connection: Ensure the scan tool connector is fully and correctly inserted into the OBD2 port. While OBD2 ports are keyed to prevent upside-down insertion, it’s still worth double-checking the connection.
- Software/Compatibility issues: Very rarely, a scan tool might have software glitches or compatibility problems with a specific vehicle.
If you’ve checked fuses and power/ground to the OBD2 port and are still experiencing communication problems, and especially if multiple scan tools fail, then further, more in-depth electrical diagnosis might be necessary. However, starting with these simple checks can often resolve the issue and get you back on track with your vehicle diagnostics for your 1999 Pontiac Bonneville.
Disclaimer: This information is for general guidance only and is not a substitute for professional automotive diagnosis and repair. Always consult your vehicle’s repair manual and take appropriate safety precautions when working on your vehicle.
