Answers
Oct 12, 2023 - 01:45 PM
Hi there,
If the OBD reader or scanner is faulty, it may not be able to read all the trouble codes that are stored in a vehicle's computer. It is essential to use a high-quality OBD scanner from a reputable manufacturer. The shop you went and have your car checked could be using an OBD scanner that is not updated. One reason is both OBD reader and scanner have different OBD protocols (shop might not have updated their OBD scanner). Lastly, there are two main types of OBD trouble codes. A generic and manufacturer specific. Generic codes are the same for all vehicles, while manufacturer-specific codes are unique to a particular make and model. Click this link for more info about diagnostic trouble code for the DIYer from our website resource blog. I hope this helps!
Oct 17, 2023 - 12:50 PM
Different Levels of Access: Consumer-grade OBD readers and professional-grade scanners can have different levels of access to the vehicle's control modules. Professional scanners often have deeper access to manufacturer-specific codes and can interface with more of the vehicle's systems.
Pending vs. Confirmed Codes: Some OBD readers might display "pending" codes that haven't yet triggered the check engine light, while others might only show "confirmed" codes. A mechanic's scanner might be set to only display confirmed codes.
Intermittent Faults: Some faults can be intermittent, meaning they come and go. It's possible that when your mechanic checked, the fault was not present, but it reoccurred later when you checked with your reader.
Update and Compatibility Issues: Some cheaper OBD readers might not have the latest updates or might misinterpret certain codes, especially if they're not frequently updated.
ECM/PCM Reset: If the ECM (Engine Control Module) or PCM (Powertrain Control Module) was reset or if the battery was disconnected, the codes might have been temporarily cleared. They could return if the underlying issue wasn't resolved.
Used ECM Issues: Since you mentioned replacing the ECM with a used one, there's potential for inherited issues. The ECM might have had stored codes or issues from its previous vehicle. Furthermore, certain components, especially like the ECM, may need to be programmed specifically for your vehicle even if they are the correct part number.
Communication Errors: U-codes, like the U2500 and U2802 you mentioned, typically relate to communication errors between modules. These can be especially tricky because they might not always be present or might not be recognized by all scanners.
In your situation, given that you're getting codes with your reader but not with the mechanic's scanner:
Second Opinion: Consider getting a second opinion from another mechanic or using a different professional-grade scanner to see if it reads the codes.
Document the Codes: When you see a code on your reader, document it with a date, time, and any relevant driving conditions. This can help in troubleshooting, especially for intermittent issues.
Directly Address Communication Errors: If you're consistently getting communication error codes, consider checking the wiring harness, connectors, and grounds related to the modules in question.
Consider the ECM: Since the codes returned after replacing the ECM with a used one, consider the possibility that the used ECM might have issues, or there might be a need for programming or relearning procedures.
Finally, if you're getting codes that lead to no noticeable symptoms or drivability issues and the mechanic's professional-grade scanner isn't reading them, you might be dealing with phantom codes from your reader. However, always prioritize safety and address any codes or symptoms that could affect the vehicle's performance or safety.
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