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07 Crusader 5.7 mpi, Velvet Drive transmission temperature alarm not working

R

rfdlou

Regular Contributor
My engines were delivered with the transmissions installed ready to run & they run perfectly. The trans temp switch has two terminals. One wire reads 5 volts to ground indicating that it’s powered from the ECM. The other reads 0 volts. To test the alarm I jumped the wires together. No MIL light no warning buzzer. Anyone have any ideas ?
 
makomark said:
Is your buzzer system stand alone or integrated with the ECU?
Click to expand...
Buzzers that came with the new engines & my old gauges all run off the ECU.The buzzers self test ok with ignition on. I also have the Murphy Power View display & can view fault codes (none) & just about every parameter except the transmission.
 
Tested for about a minute. I ASSumed it was a normally open switch that closed around 190. I’ll have to check if the resistance at the sender varies between cold & warmed up.
 
Found some 'factory literature". According to it, the 'sender unit' is really a switch that the ECU treats as a discrete. The factory parts list describes it as a sender and not a switch. I checked the MEFI-3 discrete list and it does have this provision. (The MEFI-5 lists an input as transmission temperature but I can't find an analog/discrete label.)

That factory literature also stated it was a 235 deg F switch, which is much hotter than the older 200 degree switches.

My thought is that the ECU does a verification and needs a few looks before it decides to set the code and sound the alarm. I'd expect a minute to be a reasonable timeframe for this to occur.

The only other suggestion is to try it again, but with the engine running. Some of the diagnostic routines (scanning the discrete inputs like overheat switches) will not execute if not needed, or may not make sense, like this one.
 
makomark said:
Found some 'factory literature". According to it, the 'sender unit' is really a switch that the ECU treats as a discrete. The factory parts list describes it as a sender and not a switch. I checked the MEFI-3 discrete list and it does have this provision. (The MEFI-5 lists an input as transmission temperature but I can't find an analog/discrete label.)

That factory literature also stated it was a 235 deg F switch, which is much hotter than the older 200 degree switches.

My thought is that the ECU does a verification and needs a few looks before it decides to set the code and sound the alarm. I'd expect a minute to be a reasonable timeframe for this to occur.

The only other suggestion is to try it again, but with the engine running. Some of the diagnostic routines (scanning the discrete inputs like overheat switches) will not execute if not needed, or may not make sense, like this one.
Click to expand...

Thanks for taking the time to find info on this. As this is a fairly new system there isn't much info available to the general public. I think i'll leave well enough alone at this point. Everything is working great. I just have to learn to trust the ECU. It knows best. Again, thanks for all your help
 
Trust your gut and other senses; the ECU only knows what it is told. if it doesn't get the whole story, it won't do the job it could.

That 'factory file' is 6+MB, if you want a copy send an email address that will take an attachment that large & i'll try to send it. It covers the bulk of the newer MEFI system.
 
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