The OBDII (On-Board Diagnostics II) port on a 1996 Chevy Astro van is crucial for diagnosing engine problems. Accessing the power wire for this port can be necessary for various tasks, including installing aftermarket devices or troubleshooting electrical issues. This article outlines a diagnostic procedure for communication failures, which can indirectly help pinpoint the OBDII power wire. Understanding the Class 2 communication network is key to this process.
Troubleshooting Communication Failures in a 96 Chevy Astro Van
A common issue in older vehicles like the 96 Chevy Astro is a loss of communication with the Powertrain Control Module (PCM) via the OBDII port. This often manifests as a “No Communication” error on a diagnostic scanner. Several potential causes exist, including wiring damage, faulty modules, or loose connections.
Splice Pack SP205: The Communication Hub
A critical component in the Astro’s communication network is splice pack SP205. This pack, located above the left footwell light under the instrument panel, acts as a junction for various data lines. By strategically shorting pins within this splice pack, you can isolate the source of the communication problem.
Diagnostic Procedure
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Locate SP205: Find the splice pack taped to the wiring harness above the left footwell light, near the back of the fuse block.
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Access the DLC: Remove the connector (“comb”) from SP205 and connect a diagnostic scanner to the Data Link Connector (DLC), which is the OBDII port.
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Test the PCM: Short pin D (Purple wire) to pin B (Dark Green wire) at SP205 using a jumper wire. If communication with the PCM is established, the problem lies elsewhere in the network.
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Isolate the Faulty Component: If communication is still absent, systematically short pins B and D to each of the other pins in SP205, one at a time. When a specific pin causes the scanner to display “No Communication,” the corresponding wire/module is likely the culprit.
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Investigate the Faulty Circuit: Once the problematic circuit is identified, check for issues like: Damaged wiring in the Class 2 data circuit. Power or ground problems affecting the associated module. * Faulty module itself.
Common causes of communication failures can include damaged wiring under the hood fuse block, issues with aftermarket radio wiring, chafed CAN bus wires, water damage to the PCM connectors, loose battery grounds, or a faulty Body Control Module (BCM).
Finding the root cause requires a systematic approach, but this process of elimination helps narrow down the possibilities. While this procedure doesn’t directly identify the OBDII power wire, understanding the communication network’s layout and troubleshooting process is crucial when working with the vehicle’s electrical system. Identifying the power wire often involves tracing back from the OBDII port itself or consulting the vehicle’s wiring diagram.
