Code 71 engine speed sensor circuit low

[Lui1152]

Hello everyone. I have posted here before and everyone has been really helpful.... thank you.

I have been dealing with issues of engine Staling and turning off
At first I thought it was fuel system issues but it was not.

I recently learned how to use the transmission light to get codes and got code 71.
After I got this code I replaced the engine (crankshaft) speed sensor but it did not fix my issue I still get the same code and still have the same issues.

I have not done anything else other than replacing the sensor.

Anyone have dealt with this before?
Any ideas?
It is a 6.5 TD with the 4l80e. (M1152)
Please

 

[NDT]

The injection pump solenoid has to get 24 volts for the engine to stay running. The circuit powering this solenoid is completely unrelated to any circuits related to the 4L80E.

 

[Action]

The speed sensor circuit also goes thru TPS and frequency converter. I have 71. Mine runs great just no overdrive. If my new frequency converter fixes it, i will let you know. I cant start it until steering box is back in.

 

[Lui1152]

The injection pump solenoid has to get 24 volts for the engine to stay running. The circuit powering this solenoid is completely unrelated to any circuits related to the 4L80E.

Thabk you for your reply.
How would this he related to code 71?
Would a faulty solenoid or lack of current (24 volts) affect the sensor?
I appreciate your answer and I am here to learn.

 

[Lui1152]

The speed sensor circuit also goes thru TPS and frequency converter. I have 71. Mine runs great just no overdrive. If my new frequency converter fixes it, i will let you know. I cant start it until steering box is back in.

Thank you for your reply

It sounds exactly like my issue. I can start the car, it revs fine. The problem is when I do transfer case in high and put the transmission in over drive, it will not move or it will start moving really slow with all the gas pedal down. Sometimes it idles bad and cuts off.

Please let me know what have you find out or how did you figure out that the TPS or frequency converter could be the issue.

I will appreciate it

 

[NDT]

Your injection pump is shot.

 

[Coug]

Stalling, turning off, and unable to move in drive sounds a lot like a fuel system issue.
Revving the engine with no load on it doesn't require very much fuel compared to trying to move it, and in H it takes more power than in L

Code 71 is a transmission issue; it has nothing to do with how the engine runs or produces power.

I think first you need to figure out why the engine is running poorly before bothering with the transmission.

 

[Retiredwarhorses]

Stalling, turning off, and unable to move in drive sounds a lot like a fuel system issue.
Revving the engine with no load on it doesn't require very much fuel compared to trying to move it, and in H it takes more power than in L

Code 71 is a transmission issue; it has nothing to do with how the engine runs or produces power.

I think first you need to figure out why the engine is running poorly before bothering with the transmission.

ditto….

 

[Retiredwarhorses]

The speed sensor circuit also goes thru TPS and frequency converter. I have 71. Mine runs great just no overdrive. If my new frequency converter fixes it, i will let you know. I cant start it until steering box is back in.

you don’t need a ste/ice frequency converter to run the transmission

 

[Action]

you don’t need a ste/ice frequency converter to run the transmission

Same wire goes to both. At the TCM, ohming the 2 wires from speed sensor is in 900s. If i disconnect the frequency converter, the same 2 wires show nothing. The sensor ohms in correct range.

 

[Retiredwarhorses]

Same wire goes to both. At the TCM, ohming the 2 wires from speed sensor is in 900s. If i disconnect the frequency converter, the same 2 wires show nothing. The sensor ohms in correct range.

i repeat….you don’t need the converter.

 

[Lui1152]

Your injection pump is shot.

Could you please elaborate more?

Thanks

 

[Lui1152]

Stalling, turning off, and unable to move in drive sounds a lot like a fuel system issue.
Revving the engine with no load on it doesn't require very much fuel compared to trying to move it, and in H it takes more power than in L

Code 71 is a transmission issue; it has nothing to do with how the engine runs or produces power.

I think first you need to figure out why the engine is running poorly before bothering with the transmission.

Thank you for your answer.

Could you please give me more ideas of what to check?

I already checked gas tank, fuel lines from tank to pump to filter (put in a new filter) and return lines. All are good with clean gas.



Thanks

 

[NDT]

Could you please elaborate more?

Thanks

Sure. You said: " I already checked gas tank, fuel lines from tank to pump to filter (put in a new filter) and return lines. All are good with clean gas. "

Knowing this, the symptoms you describe (stalling, no power, sometimes idles bad) are those of a failing injection pump.

 

[Lui1152]

Sure. You said: " I already checked gas tank, fuel lines from tank to pump to filter (put in a new filter) and return lines. All are good with clean gas. "

Knowing this, the symptoms you describe (stalling, no power, sometimes idles bad) are those of a failing injection pump.

Any ideas on how to check if the IP is the issue. Or any way to test/diagnose?

Thank you

 

[NDT]

Any ideas on how to check if the IP is the issue. Or any way to test/diagnose?

Thank you

If you are 100% certain you have good bubble free clean plentiful fuel flow to the ip and unrestricted return lines, and
If you are 100% certain you have uninterrupted 24 volts to the ip,
And your ip is over 10 years old,
it's time for an overhaul.

 

[Monkeyboyarmy]

Thank you for your answer.

Could you please give me more ideas of what to check?

I already checked gas tank, fuel lines from tank to pump to filter (put in a new filter) and return lines. All are good with clean gas.



Thanks

It's a "fuel" tank, not gas. And i hope your lines are filled with diesel and not gas.

Did you verify that the injector pump is returning fuel out of the return fitting on top of the pump?

 

[Lui1152]

It's a "fuel" tank, not gas. And i hope your lines are filled with diesel and not gas.

Did you verify that the injector pump is returning fuel out of the return fitting on top of the pump?

Sorry, yeah.... I meant fuel tank.

Yes, it is returning fuel out in that area.

 

[Action]

Low rpm will cause a code 71. So, if your engine is stumbling, that may cause it.
Fix your engine problem and see if light goes away.

 

[Lui1152]

Low rpm will cause a code 71. So, if your engine is stumbling, that may cause it.
Fix your engine problem and see if light goes away.

Could a lose belt or a shaking belt tensioner cause this issue?

I am really thinking out of the box here. I am a newbie and learning as much as I can.

Thanks