Check Engine Light, 51 Erorr

[RumPunch]

Is there somewhere good here to run through diag of check engine light codes? I have a miss/stutter (all original injectors installed after issue with aftermarket ones) now I am getting a 51 error code. Do I need the emissions manual off line?

 

[dirtymike]

Code 51 says the ECT signal failed at the high end(approximately 5.0 volts)failure mode indicates -40Deg. F.

 

[RumPunch]

thanks. So possibly failed coolant temp sensor/switch? Wouldn’t think that would cause a miss.

 

[dirtymike]

It will run the engine like its on choke, I think? ECU thinks its cold.

 

[dirtymike]

194 deg F should be .60 volts with 2.80 ohms

 

[dirtymike]

Back probe the ECT with a DVOM when warm

 

[Uncle Gump]

Yeah... check ECT sensor connector for 5 volt reference first.

If good... check resistance across sensor @ whatever temp it is at... bounce that number off an ECT temp table.

 

[Uncle Gump]

thanks. So possibly failed coolant temp sensor/switch? Wouldn’t think that would cause a miss.

Is it like a dead miss... or a random rich misfire.

 

[RumPunch]

Random miss can gag on throttle and mostly go away. But low load/throttle input in gear falls on its face.

 

[RumPunch]

4.68v key on 57.0k ohms across sensor, compare to original sensor, 58-59k ohms. Ambient temp (48 f ) this morning. I’ll trace down the signal output now.

 

[dirtymike]

test the old one in boiling water. analog meter you can watch the needle move as the water heats up.

 

[RumPunch]

See above just edited post comparing to original…

 

[RumPunch]

Back probed didn’t have enough time this morning to get it up to temp but no volts out of the second pin so I will check original in water at op temp and see then get truck up to temp and compare if ok I’ll check signal wire back to ECU.

 

[Uncle Gump]

For reference...

 

[RumPunch]

Thanks gump