Model years 92-95, through the July 95 build date. Early ECU's used socketed EPROMS, later cars had soldered in EPROMS. ECU numbers are xxxxx through xxxxx.
Early OBD1 cars (Passats and Corrados) had the scan plug underneath the shifter console and don't use an OBD2 compatible plug. There is an adapter available that lets you use the VAG-COM software on these cars.
OBD1 uses a normal plate style throttle body, and uses an external idle air control valve to control the idle. The TPS is removable and replaceable. Idle adaptation (????)
OBD1 features only a primary oxygen sensor (O2) for closed loop fuel trim. The O2 loop is disregarded at WOT.
OBD1 uses exhaust gas recirculation (EGR) to lower emissions and the minimum octane rating. There is a control solenoid, as well as a vacuum operated valve in the EGR system.
Later cars use a smog pump to lower startup emissions.
OBD1 computers only have minimal diagnostic functions and do not have datalogging capability on board. There are many OBD2 blocks that are not accessable on these ECUs.
Intake manifold is drilled for the EGR, early Throttle Body, as well as the idle air control valve. Not interchangeable with OBD2 ones without major modification.
Early production 92 cars have no check engine light, all others are equipped with one.
Model years 96-present, from the August 95 build date onward. ECU numbers are xxxxx through xxxxx.
OBD2 cars feature the scan port in the dashboard for diagnostics, as well as a check engine light in all models.
OBD2 uses a normal plate style throttle body, and uses an internal idle air control valve to control the idle. The TPS is not removable and replaceable. Idle adaptation can be done with the VAG-COM software(????)
OBD2 features dual oxygen sensors (O2). The precat O2 is for closed loop fuel trim. The post cat O2 is used for emissions. The O2 loop is disregarded at WOT.
OBD2 does not use exhaust gas recirculation (EGR).
All cars use a smog pump to lower startup emissions.
OBD2 computers only have full diagnostic functions and have datalogging capability on board. These codes can be scanned by a generic OBD2 reader, a VAG machine or the VAG-COM software package. There are many diagnostic blocks available.
Intake manifold not drilled for EGR, or the idle air control valve. Not interchangeable with OBD1 ones without major modification.
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