Manual Vs. Automatic Knock Sensor

[Majoraslayer]

Just stopped at AutoZone for a new knock sensor. They had a sensor listed for $37 and one for $57. When I asked for the $37 sensor, the counter guy said it was for a manual transmission truck. Do the manual and automatic 88-95 trucks really use different knock sensors? What's the difference and why?

 

[Orpedcrow]

I can’t confirm that they require/call for different knock sensors, but it makes some sense to me. I imagine a manual transmission to have different harmonics than an automatic being as they’re filled with real gears and shafts and not just black magic and voodoo dust.

 

[L31MaxExpress]

Difference is the resistance and ESC system used. The early models with the C3 ECM and external ESC use one resistance of sensor. The later models with automatics or manuals with P4 PCMs use a ESC system incorporated into the Memcal and a different knock sensor. The later models with manuals mostly use the old style C3 ECMs. Hence automatics and manuals using different knocks sensors.

 

[Majoraslayer]

Difference is the resistance and ESC system used. The early models with the C3 ECM and external ESC use one resistance of sensor. The later models with automatics or manuals with P4 PCMs use a ESC system incorporated into the Memcal and a different knock sensor. The later models with manuals mostly use the old style C3 ECMs. Hence automatics and manuals using different knocks sensors.

That makes a lot of sense. I have an early ECM truck, but he had a 1995 truck pulled up because I was also buying the later small starter. It may have been showing him details specific for the PCM-era '95 where the knock sensor depends on transmission type, while I had my '89 truck pulled up on the site.

 

[tayto]

93-95 manual trucks still used the older C3 ECM, fwiw

 

[L31MaxExpress]

93-95 manual trucks still used the older C3 ECM, fwiw

Only the V8 trucks. V6 used the P4s.