1988 Blazer 4X4. codes 22, 33, and 42. Lost my book. Anyone know what they are for?

22 = Throttle Position Sensor....Check tps adjustment, check the ECM connector, replace the tps.

33 = Map Sensor...Check the vacuum hoses from the MAP sensor. Check the electrical connections at the ECM. Replace the MAP sensor.

42 = Electronic Spark Timing....EST bypass circuit or EST circuit is grounded or open. A malfunctionaing HEI module can cause this code.

1988 Blazer 4X4. codes 22, 33, and 42. Lost my book. Anyone know what they are for?

My book is for 1995-2001 but here are the codes:

22 Throttle position sensor or circuit - voltage low

33 MAP sensor signal - Voltage High

42 Bypass or Electronic Spark Timing (EST) circuit

thanks