Experiencing a “no communication” error when connecting your OBDII scanner to a Chevy Spark can be a frustrating diagnostic hurdle. This issue prevents you from accessing crucial vehicle data, hindering your ability to pinpoint the root cause of problems. If you’re facing this challenge, particularly alongside symptoms like an engine that starts and stalls, constant security and airbag lights, this guide provides a systematic approach to diagnose and resolve OBDII communication failures in your Chevy Spark.
The inability to communicate with vehicle modules via the OBDII port often points to a disruption in the data communication network, commonly referred to as the Controller Area Network (CAN) bus or Class 2 data circuit in older systems. Let’s delve into a step-by-step diagnostic procedure to isolate the source of the communication breakdown in your Chevy Spark.
Step-by-Step Diagnostic Procedure for OBDII Communication Failure
When faced with a no communication issue on a Chevy Spark, a targeted approach is essential. This procedure focuses on isolating potential short circuits or module failures that are disrupting the data communication network.
1. Locating Splice Pack SP205:
The first critical step is to locate the splice pack SP205. This splice pack serves as a central distribution point for various circuits, including data communication lines. On a Chevy Spark, SP205 is typically found taped to the wiring harness above the left side footwell light, positioned under the instrument panel (IP) on the left side, near the rear of the fuse block. Carefully accessing this splice pack is crucial for the subsequent diagnostic steps.
2. Initial Communication Test with Jumper Wire:
Once you have located SP205, disconnect the “Comb,” which is likely a connector or retaining clip holding wires in the splice pack. Now, connect your OBDII scanner to the Diagnostic Link Connector (DLC). To bypass potential issues within the splice pack and test direct communication with the Powertrain Control Module (PCM), use a jumper wire to short pin D (typically a Purple wire, check your wiring diagram for confirmation) to pin B (Dk Green wire) on the DLC. Attempt to establish communication with the PCM using your scanner.
3. Isolating the Faulty Circuit or Module:
If communication is established in the previous step, it indicates that the PCM and the basic communication lines are functional. The issue likely resides in a module or circuit branching off from the splice pack SP205. To pinpoint the culprit, use another jumper wire to sequentially short pins B and D on the DLC to each of the other pins in SP205, one pin at a time.
Observe your scanner’s communication status after each short. If, when shorting pins B and D to a specific pin in SP205, the scanner displays “No Communications,” this indicates that the wire or module connected to that pin is the source of the communication failure. This short circuit is dragging down the entire data communication network, preventing communication.
4. Investigating the Faulty Module/Circuit:
Once you have identified the pin in SP205 causing the communication failure, trace the corresponding wire to the module it connects to. At this module, thoroughly inspect the Class 2 data circuit wiring, as well as the power and ground connections to the module itself. Common issues to investigate include:
- Wiring Damage: Look for signs of chafing, cuts, or corrosion in the wiring harness leading to the module. Pay close attention to areas where the harness might rub against metal components or sharp edges.
- Connector Issues: Inspect the module’s connector for corrosion, bent pins, or loose connections. Ensure the connector is securely seated.
- Module Power and Ground: Verify that the module is receiving proper power and ground. Use a multimeter to check for voltage and ground continuity at the module’s power and ground pins. Refer to a wiring diagram for pinout information.
- Internal Module Fault: While less common, the module itself could be internally faulty and causing a short circuit on the data line. Consider this possibility after ruling out wiring and connection issues.
Common Causes of OBDII No Communication on Chevy Spark
Troubleshooting OBDII communication problems can sometimes feel like chasing ghosts, as various issues can lead to the same symptom. Based on reported fixes and common automotive electrical problems, here are some potential causes to consider when diagnosing a Chevy Spark with no OBDII communication:
- Wiring Damage Under Hood Fuse Block: Inspect the wiring harness around and under the under-hood fuse block. This area is exposed to the elements and engine heat, making it susceptible to wiring damage, corrosion, and rodent intrusion.
- Aftermarket Radio Wiring Issues: Improper installation or faulty wiring of aftermarket radios is a frequent cause of data communication problems. Aftermarket radios can sometimes interfere with the vehicle’s data bus if not correctly integrated. Check the radio wiring and any associated adapters or interfaces.
- CAN Bus Wire Rubbed Open on Negative Battery Cable: Carefully examine the CAN bus wiring harness, particularly where it runs near the negative battery cable or any other grounding points. Rubbing against these points can wear through the wire insulation, causing a short circuit to ground and disrupting communication.
- PCM Connector Water Intrusion: Inspect the PCM connectors for signs of water intrusion or corrosion. Water can seep into connectors, causing shorts and communication failures. If water intrusion is evident, thoroughly clean and dry the connector and pins. Consider using dielectric grease to prevent future moisture issues.
- Loose Battery Ground: A loose or corroded battery ground connection can cause a wide range of electrical problems, including communication issues. Ensure the battery ground cable is clean, tight, and securely connected to the vehicle’s chassis.
- Faulty BCM (Body Control Module): In some cases, a failing BCM can be the root cause of no communication. The BCM is a gateway module that often plays a role in data communication. While BCM replacement is sometimes necessary, it should be considered after thoroughly investigating other potential causes.
Conclusion
Diagnosing OBDII no communication issues on a Chevy Spark requires a systematic and patient approach. By following the outlined diagnostic steps, focusing on splice pack SP205, and meticulously inspecting wiring and module connections, you can effectively isolate the source of the communication breakdown. Remember to consult wiring diagrams specific to your Chevy Spark model year for accurate wire colors and pin locations. By methodically eliminating potential causes, you can restore OBDII communication and proceed with further diagnostics and repairs.
