Diagnostic Aids

With ignition on and engine off, manifold pressure is equal to atmospheric pressure and signal voltage will be high. This information is used by ECM as an indication of altitude and is referred to as BARO. To check sensor, compare BARO reading with a known good vehicle with the same sensor. Readings should be the same within .4 volt.

Code 33B will result if circuit No. 452 is open, or if circuit No. 432 is shorted to voltage or circuit No. 416. For intermittents, see INTERMITTENTS in H - TESTING W/O CODE - EFI article.

Fig 1: Code 33B: MAP Sensor (Signal Volt Lo) Circuit Diagram

Courtesy of ISUZU MOTOR CO.

Fig 2: Code 33B: MAP Sensor (Signal Volt Lo) Flow Chart

Courtesy of ISUZU MOTOR CO.