On-Board Diagnostics (OBD) — Quick Facts (Chevrolet Tahoe 1)

1. Failure of sensors and devices of some emission control systems can affect the performance of the engine. Reading diagnostic codes and accurately identifying the specific faulty device is possible thanks to the use of the OBDI on-board diagnostics system on the vehicle (until 1995.) or OBDII (since 1996). To read diagnostic trouble codes in this system and identify them, special expensive scanners are required, so it is advisable to perform all types of diagnostic, repair and adjustment work in a car service center.

2. On models before 1995, diagnostic codes are read from the processor unit memory by connecting to the ALDL connector, which is located under the driver's instrument panel (see photo). Some vehicles equipped with 4L60-E or 4L80 electronically controlled automatic transmissions are equipped with the ability to read additional transmission fault codes. The processor unit on these models works in conjunction with the programmable memory unit (EPROM) and the emergency fuel supply unit (CALPAK).







3. On models since 1996, a single processor unit PCM is installed, which provides control of the power unit (engine and transmission).

4. Diagnostic codes must be checked after the SERVICE ENGINE SOON indicator lamp on the instrument panel starts to glow.