Need help after changing fuel filter

[GaryDoug]

Use the shbox.com site for your codes. http://shbox.com/1/Dtcs.htm
Or use the 94 F-car factory service manual.

DTC 43 is : Knock Sensor (KS) circuit
DTC 23 is : Intake Air Temperature (IAT) sensor circuit (signal voltage high, low temperature indicated)

Neither is likely anything to do with the pcm. Check the connectors of both. If ok, replace the sensors.

[Superfly9c1]

After checking in my Haynes Repair Manual, it says code 43 is the PCM not receiving a knock sensor response. Could it be that the PCM needs reprogrammed?

[Injuneer]

DTC 43 means the voltage on the single-wire knock sensor circuit is not within the specified range (0.78 - 4.10 volts). Should not affect the starting. When DTC 43 sets, the PCM retards timing based on engine operating conditions, but that's with the engine running.

Easy to check the circuit. Key on/engine off pull the harness connector of the knock sensor. Measure the voltage between the single conductor in the connector and the engine block. Should be 5 volts. Connector still off the sensor, measure the resistance between the pin on the sensor and the block. Should be about 3,500 - 4,500 ohms. Put the connector back on the sensor, check voltage between the wire and the block, should be in the range of 1.5 - 3.5 volts.

In general, it's better to use LT1-specific sites like Shoebox, rather than Haynes or Chilton.