Decoding Car Diagnostics: Understanding OBD-I Fault Codes

Navigating the complexities of car diagnostics can seem daunting, especially when faced with unfamiliar terminology. You might be wondering, “What Does A Floco Mean In Car Diagnostics?” While “floco” isn’t a standard term in automotive diagnostics, it’s possible it’s a misunderstanding or a less common way to refer to fault codes or error codes that your car’s computer system generates. In the realm of car diagnostics, understanding these codes is the first step to identifying and resolving issues. This article will guide you through the basics of car diagnostic codes, specifically focusing on the OBD-I system, which was prevalent in vehicles from 1988 to 1995. We’ll explain how to read these codes and what they signify, empowering you to take a more informed approach to your vehicle’s maintenance.

Understanding OBD-I and Diagnostic Codes

On-Board Diagnostics I (OBD-I) was an early generation of automotive diagnostic systems. Its primary function is to monitor various vehicle systems and alert the driver to potential problems through the “Service Engine Soon” light (often referred to as the check engine light) on the dashboard. When the system detects an anomaly, it stores a diagnostic trouble code, which is essentially a numerical representation of the issue.

These codes are invaluable for mechanics and car owners alike as they provide a starting point for diagnosing problems. Instead of blindly guessing what might be wrong, a diagnostic code points towards a specific area or sensor that requires attention.

Reading OBD-I Codes Manually

One of the great aspects of OBD-I systems in older vehicles is the ability to retrieve these diagnostic codes without needing specialized scan tools. You can do it yourself with just a simple paper clip or a short piece of wire. Here’s how:

Locate the DLC Connector: The Diagnostic Link Connector (DLC), also sometimes called the Assembly Line Diagnostic Link (ALDL), is usually found under the driver’s side dashboard.

Image: Diagram showing the A & B terminals on an OBD-I DLC connector, highlighting the location for jumpering.
Jumper the A and B Terminals: With the ignition switch turned off, use your paper clip or wire to create a connection between terminal A and terminal B on the DLC connector. These terminals are typically located at the top right of the connector, as shown in the image above.
Turn the Ignition On: Turn the ignition switch to the “ON” position, but do not start the engine. Observe the “Service Engine Soon” light on your dashboard.
Interpret the Flashing Codes: The “Service Engine Soon” light will begin to flash in a pattern. This pattern represents the diagnostic codes. Code 12 is the starting point and is considered a normal system check, indicated by a flash, pause, flash flash (one flash, a pause, then two flashes).
Code Repetition: Each diagnostic code will be displayed three times before moving on to the next code in numerical order. The entire sequence of codes will repeat continuously until you turn the ignition off.
Code 12 is Normal: It’s important to remember that code 12 is not an error. It simply indicates that the diagnostic system is functioning correctly and is initiating the code display sequence.

Common OBD-I Trouble Codes for Gasoline Engines

Here’s a list of common OBD-I codes related to gasoline engines. Keep in mind that not all codes apply to every system, and this list is not exhaustive. If you encounter a code not listed here, consult a repair manual specific to your vehicle or seek professional assistance.

13 – O2 (Oxygen Sensor) circuit open
14 – ECT/CTS (Engine Coolant Temperature) sensor circuit low (high temperature)
15 – ECT/CTS (Engine Coolant Temperature) sensor circuit high (low temperature)
16 – VSS (Vehicle Speed Sensor) buffer fault
21 – TPS (Throttle Position Sensor) circuit high (signal voltage high)
22 – TPS (Throttle Position Sensor) circuit low (signal voltage low)
24 – VSS (Vehicle Speed Sensor) circuit low
28 – TR (Transmission Range) pressure switch assembly
32 – EGR (Exhaust Gas Recirculation) valve error
33 – MAP (Manifold Absolute Pressure) sensor circuit high (low vacuum)
34 – MAP (Manifold Absolute Pressure) sensor circuit low (high vacuum)
35 – IAC (Idle Air Control) error
36 – Idle speed control actuator error (when equipped)
42 – IC (Ignition Control) error
43 – KS (Knock Sensor) error
44 – Lean exhaust
45 – Rich exhaust
51 – PROM (Programmable Read-Only Memory) error (memcal, chip)
53 – System voltage high (supply to ECM/PCM)
54 – Fuel pump relay circuit low voltage
55 – ECM/PCM (Engine Control Module/Powertrain Control Module) error

Important Considerations About Diagnostic Codes

It’s crucial to understand that a diagnostic code is merely a starting point in the troubleshooting process. It indicates a potential issue within a system or sensor, but it doesn’t definitively pinpoint the exact cause. For example, a code indicating an oxygen sensor circuit problem might be due to a faulty sensor, wiring issues, or even problems in related systems.

Therefore, further investigation is always necessary. Think of the code as a direction, not the final answer. A skilled technician will use the code in conjunction with other diagnostic techniques, such as visual inspections, sensor testing, and symptom analysis, to accurately identify the root cause of the problem.

Clearing OBD-I Codes

After addressing the issue that triggered the diagnostic code, you’ll want to clear the code and turn off the “Service Engine Soon” light. For OBD-I systems, this is typically quite simple:

Battery Disconnection: Disconnecting the negative battery terminal for about 20 seconds will usually clear the stored codes.
Automatic Clearing: OBD-I codes will also automatically clear after approximately 50 engine starts if the problem that caused the code has not reoccurred.

Conclusion

Understanding car diagnostic codes, whether you call them “flocos” or fault codes, is a valuable skill for any car owner. For older vehicles equipped with OBD-I systems, reading these codes manually is a straightforward process that can save you time and money in diagnosing car problems. Remember that while codes provide a helpful starting point, thorough diagnostics are essential for accurate repairs. As automotive technology advances, modern vehicles utilize more sophisticated OBD-II systems and scan tools, but the fundamental principle of using diagnostic codes to guide troubleshooting remains the same.