I have problem with 966H Caterpillar WHEEL LOADER Neutralizer Pedal Position Sensor

[mante]

Hi All,
I have a mysterious problem with 966H Caterpillar WHEEL LOADER BJ601568*
that is need to after 3 or 4 weeks to re-Calibration with code

737-13 Neutralizer Pedal Position Sensor : Out of Calibration ....

Actually they changed Pedal Position Sensor and they called me to investigate the problem after calibrated the pedal .... it's come again and I rebooted the calibration but after 3 weeks comes again ....

if there any producer to do this calibration or if there is any problem from electrical side please provide me

Thanks

 

[Nige]

First thing I would be looking at is the pedal pivot linkage and the linkage that connects between the left (neutralizer) pedal and the right (brake) pedal. They often get full of dirt/mud and stick. Similarly the left/right pedal pivots can stick.

Check the stop at the rear of both pedals (arrow on left) is not full of dirt and check that the pivots on both bpedals (arrowed) are free and lubricated. Also make sure the link between the two pedals can rotate freely.

 

[mante]

Thanks for reply
Ok ,but do i need to calibrate to erase the code ....
note: the wheel loader now is not moving.

 

[Nige]

Right now the 737-13 Code is Active. The only way it can be erased is by first carrying out a successful calibration.
Once the sensor has been calibrated successfully the 737-13 will change status from Active to Logged and at that point it can be erased.

Just to make sure that you do not have a harness/connector fault try making the PWM sensor signal test (attached) and see if it throws up any anomalies.

 

[mante]

Ok Boss
I will use this Procedure tell me if it's right .....


Position Sensor (Left Brake Pedal) (Electronic Technician) - Calibrate
Media Number -UENR1625-01
Thanks

 

[Nige]

That's the one.

But before you do it, make all the checks listed above - that everything including the shaft in between the two brake pedals is free to move and that there is no dirt or caked mud around the back end of the pedals.

 

[mante]

Don't worry I will do it

Thanks Boss

 

[mante]

Hi,
I pass through the all stepes and I found problem the voltage between signal and ground contacts at the machine harness connector for the sensor is 5 volt for Position Sensor (Left Brake Pedal) and the park brake pressure sonsor .... The Logged codes recorded 737-4 737-13 ....

Do you think the ECM is failed or i should doing some test before decide?

Thanks for help

 

[Nige]

Here's the schematic for your machine.

The LH pedal sensor is somewhat unusual in that it is supplied with Batt+ 24v rather than 5v or 8v stabilized from the ECM. This supply comes from the fuse box.

I suggest that you disconnect the sensor from the machine harness and try following the 164 power wire in the backwards direction from the LH pedal sensor towards the fuse box. You should have 24v between that wire and the machine chassis.

If that shows nothing, try the continuity in the 202 Black wire from the sensor connector to machine frame ground.

Then check continuity in the G746 whitre wire all the way back to the ECM.

NOTE: The electrical schematic Page 9, the wire carrying power to the LH pedal sensor (Grid H-1) is identified as 164-C264 White. If you follow that wire back towards the fuse box there is a splice to wire 164-C276 White at Grid D-12. Follow that wire and it changes ident to 164-E7 White at CONN 35. That wire takes you to Grid H-6 where it splits into 3 wires. Those 3 wires become 164-E19, 20, & 21. Those wires power the three implement lever postion sensors located at Grid H-7. Try disconnecting all those three sensors and see if the problem on the LH pedal sensor goes away.

 

[Nige]

Sorry, forgot the schematic.

 

[mante]

Thanks for reply and explain

But The 5 volt is not from supply voltage ..... is from the signal wire G746 and C491 should be 8 volt for both signal that supplied by ECM

 

[mante]

Sorry, forgot the schematic.

Thanks a lot

 

[Nige]

Check the schematic. The supply voltage to the LH Pedal sensor (amongst others) doesn’t come from the ECM. It comes from the fuse box and is 24v.

The G746 signal wire from the pedal sensor will carry a PWM signal that would be measured by putting a DMM in the duty cycle mode. The output will be a percentage not a voltage

This is somewhat different to what I’m used to where PWM-type sensors like this one are supplied with stabilized power at either 5v or 8v from the ECM. In those cases the sensor “ground” wire goes back to the ECM. In the case of the LH pedal sensor the 202 Black wire is grounded to the machine frame, not a return back to the ECM.

I must admit it took me a while studying the schematic before I could get my head around how it works.

 

[mante]

Check the schematic. The supply voltage to the LH Pedal sensor (amongst others) doesn’t come from the ECM. It comes from the fuse box and is 24v.

The G746 signal wire from the pedal sensor will carry a PWM signal that would be measured by putting a DMM in the duty cycle mode. The output will be a percentage not a voltage

This is somewhat different to what I’m used to where PWM-type sensors like this one are supplied with stabilized power at either 5v or 8v from the ECM. In those cases the sensor “ground” wire goes back to the ECM. In the case of the LH pedal sensor the 202 Black wire is grounded to the machine frame, not a return back to the ECM.

I must admit it took me a while studying the schematic before I could get my head around how it works.

The supply voltage is 24v
The signal voltage is 5v from harness sensor connector
OK Boss

 

[Nige]

The signal voltage is 5v from harness sensor connector.

As I said before, you have to measure the output signal from the sensor as a duty cycle percentage, not a voltage. To measure the percentage requires a DMM capable of measuring duty cycle (the square wave signal that is put out by the sensor) and not all DMMs have that capability.

 

[mante]

I have one question about this test
737-4 i got this at logged
and I did this test



I found the voltage is 5 volte less than the suspected 8 volte....
What do you think for this test ?

Thanks Boss

 

[Nige]

I’ve read that document from start to finish and unless someone else says different I’m sure it applies only to sensors powered by stabilized 8v from the ECM.

The pedal position sensor is powered by 24v and not from the ECM.

I’m going to do some more research regarding troubleshooting the 24v sensors. Until I get some concrete information humour me - try disconnecting the three control lever position sensors and see what happens to the pedal position sensor code.

 

[mante]

Ok Bro .... you will do a big favor for me ..... really it's confuse me the supply voltage is 24 volt but the signal voltage is 5 volt not as per instruction says should be 8 + - 0.5 Vdc

Thanks for help

 

[Nige]

I needed to sleep on this.... based on my experience with PWM sensors I am convinced that document does not apply to these particular sensors on your machine. Also there is an error in it even for the 8v-type of sensor.
Below I will attempt to explain why I think this. I've taken your snip but added a couple of highlights to it.

NOTE: See steps A & B. You have the power ON and the sensor is disconnected from the machine harness. In this state all that can be measured is sensor supply voltage.

Note the comment highlighted in red Step C. "Refer to the schematic to determine the voltage source for the suspected sensor." The voltage source for these sensors is the fuse box - 24v. (remember I already said that most PWM sensors are supplied with 8v from the ECM and are also grounded back to the ECM. Yours are NOT, they are 24v.)

I think Step D (highlighted blue) should read - "Measure voltage between the sensor supply and ground contacts at the machine harness cannector for the sensor.
Why do I say this.? Because in the 3rd column the last two points (NOT OK + Repair) states "......the open or short will be on the power or ground wires. Repair or replace the machine harness."

So the question is why would you test voltage between signal & ground wires to determine a potential fault between power & ground wires...? Hmmmm......

Basically this document (well this particular step anyway) is foobarbed and I should have read it throoughly before posting it. My apologies for that.

The test this step is actually performing is sensor power test that you have already measured as 24v which is correct according to the schematic.

 

[Nige]

Below is what I think that the text of this step of the diagnostic ought to look like.
I've included a clip from the schematic showing the sensor.