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Curtis B.
Curtis B., Technician
Category: Construction and Road Equipment
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Experience:  Technican turned service manager with multiple lines of equipment and rental units.
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I am working on A Cat D250E Articulated truck PIN#5TN01600

Customer Question

I am working on A Cat D250E Articulated truck PIN#5TN01600 Transmission # ***** . I am having problems with the automatic transmission. When i put it in drive it will only stay in low gear no matter what gear i put it in. When in reverse it will work in reverse high and reverse low. When we by passed the electrical system and moved the gears manually all gears work. We took the ECM for the transmission to a shop to get it looked at they said it was working properly. I am also getting 24V at up solenoid. The lock up solenoid and down solenoid read 4.6V.
JA: Thanks. Can you give me any more details about your issue?
Customer: When we switch the Up and Down solenoids the transmission will stay in high and will not go to a low gear.
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Submitted: 11 months ago.
Category: Construction and Road Equipment
Expert:  catmastertech replied 11 months ago.

Hello,

Did you check for fault codes?

If so, what did you find?

Have you tested the TOS (transmission output speed) sensor?

Expert:  catmastertech replied 11 months ago.

Do you know if the bed switch or hold switches are working?

Customer: replied 11 months ago.
Thanks for helping.
The ECM for the transmission has a display screen that shows logged codes:
602-F03
681-F03
681-F04
700-F02
700-F07
702-F02
707-F03
707-F05
707-F06 *
708-F05 *
709-F03
709-F05We also did not test the TOS. What are ways I can test it with a DMM?
Also in the the cab the Transmission warning lamp is on.
Customer: replied 11 months ago.
The bed switch for the dump works not sure about the hold switch.
Expert:  catmastertech replied 11 months ago.

The best way to test the TOS is to use the ECM. Attached is a file to show each mode and a complete list of fault codes.

I am assuming the codes with * are the active codes. I would focus on these first.

Do you have a service manual?

The hold switch may not be shown on this display, some had it and others did not.

Expert:  catmastertech replied 11 months ago.

Did you swap the solenoids for up and downshift or the coils? (or did you just switch the wires?)

Do you have a service manual?

Will you be needed more help on this?

Customer: replied 11 months ago.
I need more help my computer just turned off. Now im back on
We switched solenoids and wires both solenoids are new and when connected to the up shift circuit it will read 24V
I do not have a service manual.
Expert:  catmastertech replied 11 months ago.

Ok, thanks for the reply.

Here are details for the 707 and 708 codes. Use the FMI number for the active code (707-F06 = FMI06).

Same for 708-F05 (FMI05)

(see attached file)

Please let me know what you find and if you need further help.

Customer: replied 11 months ago.
I performed the test everything was in specification. How many volts should I be reading at solenoids?
Expert:  catmastertech replied 11 months ago.

When EPTC II decides to shift, the corresponding solenoid is activated with +battery voltage until the shift occurs.

If battery voltage is 24 volts with engine running, then you should get 24 volts at the corresponding solenoid.

Expert:  catmastertech replied 11 months ago.

Did you see the TOS sensor working?

Are the same codes still present?

Try clearing the codes and see which codes return.

Newer models, the retarder lever or vale has a pressure switch that can hold shifting. I am not sure this older machine would have one but, it is something to check if it applies.

Expert:  catmastertech replied 11 months ago.

Also verify P2 pressure switch is working using the monitor screen on the ECM.

Customer: replied 11 months ago.
I cleared the codes and no codes came back. I verified that the TOS is working.
No codes are being shown on screen now. Ran machine but we still have the same problem.
The down shift solenoid shows 24 V when shifting to R1 R2. Up Shift solenoid shows 24V when shifting into D or 1 but wont show 24 V when I move the shift lever to 2 3 4. We raised the RPM in D and it doesnt want to get out of 1st.
Also the transmission warning lamp is still on and stays on the whole time.
Expert:  catmastertech replied 11 months ago.

The transmission must reach the correct speed for the ECM to shift to the next gear. For this to happen, the lockup clutch must engage so the transmission is in direct drive. This will get the output speed high enough to select the next gear.

P2 pressure signals the ECM to engage the lockup clutch. It must work for correct shifting.

The engine must also turn fast enough for all of this to work. If the throttle pedal or cable does not reach full speed, nothing else will either.

Expert:  catmastertech replied 11 months ago.

The schematic shows you have a retarder switch, I haven't found a particular test for it yet.

Here is a shift point chart.

Expert:  catmastertech replied 11 months ago.

The normal shiftpoints for Articulated Trucks are listed in the following tables. To help protect the power train, certain shifting restrictions exist. The major shifting restrictions are described in the following paragraphs.

Engine overspeed protection exists. If engine speed increases to approximately 2900 rpm, the transmission will upshift one gear. And if in top gear, the lockup clutch will be disengaged which places the machine in torque converter drive.

Engine underspeed protection exists. If engine speed decreases to approximately 750 rpm, the transmission will downshift one gear.

Retarder protection exists. When the retarder is applied, all shift points are elevated. This increases engine speed which causes more oil to flow through the retarder. For upshifts, the shiftpoint is elevated approximately 250 engine rpm. For downshifts, the shiftpoint is elevated approximately 75 engine rpm.

Transmission protection exists. For 2.3 seconds after a shift, the transmission will not shift in the opposite direction. For example, after an upshift, a downshift is not allowed until 2.3 seconds have passed. This is called the anti-hunt feature and eliminates shifting due to minor ground speed fluctuations near a shiftpoint. The 2.3 second restriction allows conditions to stabilize before an opposite shift. If any brake is applied, the anti-hunt feature is canceled and transmission downshifts occur as conditions demand.

Neutral coast protection exists. When NEUTRAL is selected at the shift lever while the transmission is in a forward gear, the transmission will only be shifted to neutral when ground speed is 5 mph or less. If the machine is coasting with the transmission in NEUTRAL, the transmission will not shift into a forward gear. The transmission will only shift to REVERSE when ground speed is less than 3 mph.

Customer: replied 11 months ago.
What would cause the warning lamp for the transmission to stay on?
We brought the engine RPM up to 1800 RPM in first gear and it still does not up shift.
We also have replaced the P2 pressure switch.
What are ways to test the lock up solenoid?
Expert:  catmastertech replied 11 months ago.

Can you be specific as to which light is on and which panel it is located?

If you can upload a photo of the light, that may help too.

Expert:  catmastertech replied 11 months ago.

Does the TOS signal reach the desired speeds?

Expert:  catmastertech replied 11 months ago.

Pressure testing is the best way to know if the lockup clutch is working.

Customer: replied 11 months ago.
TOS is 26 on ECM.
Warning light is bottom right.
Expert:  catmastertech replied 11 months ago.

The TOS light will flicker when it is receiving a signal. You need to place the ecm into mode 7 to view the actual speed. (instructions were in the first attachment.)

The yellow light is just a warning for the EMS panel.

(Action Light (6) - Indicates that action must be taken in response to a warning from the EMS system.)

The EMS panel red light is for the transmission oil temperature, not an ECM fault.

(Transmission/Retarder Oil Temperature (5) - Indicates excessive transmission/retarder oil temperature which may be due to driving in the wrong gear or improper use of the retarder. If the indicator remains on, stop the machine at a convenient location and investigate the cause.)

Customer: replied 11 months ago.
I put the ECM in mode 7 and the TOS reads 26 when i am at high RPM in drive.
Customer: replied 11 months ago.
The transmission/Retarder oil temp lamp stays on. At first start up in morning the lamp will be on even when oil is not.
Expert:  catmastertech replied 11 months ago.

Does it change from 0 and move smoothly up as you increase speed?

Have you checked the wiring to the transmission oil sensors?

Customer: replied 11 months ago.
it moves up smoothly from 0 to 26. Is 26 too low for the TOS?
I have not checked the wiring for the oil transmission sensor.
Expert:  catmastertech replied 11 months ago.

The image of the display appears to show the retarder light is on. This light should be off.

Yes, it should exceed 171 to shift to 1 lockup then to 287 to shift to 2. (refer to shift point chart.)

Customer: replied 11 months ago.
Ok do you think the TOS could be the problem? I am thinking about buying the TOS monday.
I will do further diagnosis on the vehicle Monday.
Customer: replied 11 months ago.
The TOS reads 26 on the ECM but the drive shaft turns an estimate of at least 150 RPM.
Expert:  catmastertech replied 11 months ago.

The TOS must start from 0 and then move up as speed increases. I believe you are not in the correct mode and this is just the harness code. (nothing important yet) This is a pulse signal and does not correspond to actual driveshaft speed.

The sensor may have a fault but, these machines always have wiring issues. That is what must be fixed first.

Your status lights should not be on, this will prevent shifting. The body lamp, retarder lamp and service brake lamps should be off. The TOS lamp is can be on but, it should flick as the speed signal comes in.

Attached is another file with more details about the status lamps and service modes.

I hope this attachments are helping, if not please let me know.

Customer: replied 11 months ago.
Thank you I will continue working on this monday.
Expert:  catmastertech replied 11 months ago.

You're welcome. Just keep me posted of what you find. I will not be available until the night time as I too will be out working and have very limited access to the site.

I will be glad to help all I can.

Customer: replied 11 months ago.
Hey, good afternoon. I found the retarder oil temperature sensor and the sensor was tore apart. I located the wires for the sensor and by passed the sensor, the warning light for the retarder oil temp turned off. I am Ordering a new sensor now. I removed the drive shafts and tried to operate the transmission with the warning lamp off and the wires by passed but I still have the same problem. On the ECM at idle the TOS shows 8 (80), when I raise the RPM the highest the TOS will get to is 26 (260). What should I look for now?
Thank you for your time.
Expert:  catmastertech replied 11 months ago.

TOS speed is still too low, engine speed must be too low.

TOS speed needs to get to about 290 to make the shift to 2nd.

Verify engine speed can reach 2400 rpm.

Do you still have fault codes present?

Which status lights on on when you are running the machine and trying a shift?

Expert:  catmastertech replied 11 months ago.

Also, have you tested the lockup clutch pressures? (or solenoid for working?)

Customer: replied 11 months ago.
No I have not tested the lock up clutch pressure or solenoid. What are ways I can test that?
There are no active fault codes shown on ecm.
When vehicle is in neutral no lights are shown on the panel but the (p) light for parking brake. When put in drive with the parking brakes button pushed in the yellow warning light for the ems(!) Comes on and off repeatedly and the red (p) parking brake light stays on. We checked the solenoid at the parking brake and it is working.
The highest RPM the engine will get to is 2250 RPM. TOS still shows 260.
Customer: replied 11 months ago.
We checked for amount of pressure at p2 pressure it is 0 psi in neutral and 300 psi in Drive at any rpm.
Expert:  catmastertech replied 11 months ago.

The yellow light is not an ECM warning light. It is call the Action Light.
Action Light - Indicates that action must be taken in response to a warning from the EMS system.
The EMS system is the panel to the right. The light is flashing, warning you the parking brake is not released and the transmission is in gear.
The solenoid is only one part controlled by the switch. It has a seperate section that sends a signal to the ECM and EMS that the button is in the released position.
You should check the wiring for this section of the park brake button for a broken wire or loose connection.

The engine speed must turn 2400 rpm. Check the linkage for wear then try adjusting the high idle stop screw to obtain the correct speed. If it cannot be changed, check the engine for power loss or problems with the fuel system. (I have even seen air filters or leaking aftercoolers cause the issue.)

Attached is testing procedures for the lockup clutch.

Customer: replied 11 months ago.
What is the max RPM for the engine that is suppose to be in the vehicle?
Expert:  catmastertech replied 11 months ago.

2400 rpm

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