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Curtis B.
Curtis B., Technician
Category: Construction and Road Equipment
Satisfied Customers: 989
Experience:  Technican turned service manager with multiple lines of equipment and rental units.
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I have a cat it28g that every now and then when I put it in

Customer Question

I have a cat it28g that every now and then when I put it in forward or reverse it won't move.
Submitted: 1 year ago.
Category: Construction and Road Equipment
Expert:  catmastertech replied 1 year ago.
Sorry, I could not reply earlier. I was out in the field working today and do not have internet access.I would check your other override switches. Try using the transmission neutralizer first and see if you can deactivate the left brake declutch action. Sometimes the switches in the pedal can fail. Overriding the feature will bypass the switch and should restore drive.Also, if you have Auto-shift switch, turn it off to bypass the ECM shift control. If a speed sensor is not working, this could cause the ECM to disengage the transmission.If you need further help, please post the full machine serial number with your reply. Post the results of these tests and so I can see if you have located the issue or not.
Customer: replied 1 year ago.
Hello, the serial number on my machine is 8cr02202. Let me explain this in a little more detail. On the morning I got hold of you I had just changed the parking brake safety switch. I ran the machine for a couple hours. While running it I would occasionally stop and put it in neutral and apply the parking brake. I didn't have any problems. When I finished with the machine I stopped put it in neutral and back into gear and it wouldn't move. I tried forward and reverse at least 10 times occasionally shutting the machine all the way down and restarting it. It just wouldn't move.
This morning I went out to try the things you told me to do but when I started it, it moved as soon as I put it in gear. I used it for about a half hour, stopping and starting and using the parking brake. When I parked it, it was working fine.
I came back about an hour later which is right now and it won't move again.
When it's moving there is no slippage and everything works well. I have noticed every once in a while my brake pressure warning light comes on. A guy told me how to test that and it seems it's the brake accumulator. I'm not sure if the 2 could be related. I have recently sold the machine and I'm just waiting for the check to clear but I don't want to give it to them like this. I hope this gives you more to go on. Thanks, Mike.
Customer: replied 1 year ago.
After typing out my last response I went right out and tried the lift again. As soon as it started it was able to move again. I ran it up the road from my house to my shop (about 20 minutes in 4th gear and almost full throttle) when I got there I put it in neutral and applied the parking brake several times and the tranny engaged fine. I shut it down for about an hour and tried it again and it wouldn't move. I can't see any pattern like if it only does it when warm or cold. It just seems to be random. I think I should add that when I first got the lift about 2 years ago, I would notice sometimes, when I put it in gear the tranny wouldn't engage but I just put it in neutral and back in drive and it would move. I always thought it was just some safety switch that wasn't working properly. It seems as though it is a progressive thing.
Expert:  catmastertech replied 1 year ago.
Thanks for the serial number, that helps me see some of the options this machine has.I just want to be certain the transmission neutralizer override switch on the left front dash panel is working correctly. In one position the transmission stays engaged regardless of the brake pedal position and when the switch is in the other position, the transmission will disconnect when the brake pedal is applied. Please verify this is correct. If it is, look at the parking brake switch again. The switch is not the only thing that can fail. The wiring could also be a problem. If the direction control lever or the direction control switch (if equipped) is put in the FORWARD position or the REVERSE position before the parking brake is disengaged, then the machine will not move. Move the direction control lever or the direction control switch (if equipped) to NEUTRAL. Release the parking brake. Then, move the direction control lever or the direction control switch (if equipped) to the desired direction in order for the transmission to be engaged.If you shift quickly out of gear and back in, this can override the parking brake switch but, you should hear an alarm indicating the brake is applied and the parking brake lamp should also be on. (This is assuming all the electrical is working correctly.)If this is correct, then we must look at the diagnostic lamp at the transmission ecm to see if a fault code is present. This is located under the cab on the right side below the fuse panel. You will need to remove the side cover to see under the cab. Information is shown on diagnostic indicator by flashing the indicator ON and OFF. The information that is flashed represents a two digit number. There is a series of flashes that represent the first digit. This is followed by a one second pause. The final step is a series of flashes that represents the digit in the second position. Count the number of flashes in order to determine each digit. A pause of about three seconds separates each two digit number.The ECM uses the diagnostic indicator in two different modes. The two modes are given below:Normal ModeService ModeWhen power is applied, the ECM enters normal mode. Removing the machine identification plug from harness code connector 4 places the ECM in the service mode. Once in service mode, grounding different connector contacts of the harness code connector causes the ECM to flash diagnostic codes on the indicator. This diagnostic code is a two-digit number that corresponds to the normal Caterpillar service codes.Harness code connector 4 is located under the platform on the right side of the machine. The connector provides access to the service inputs. Connector contact 1 is grounded to flash diagnostic codes for active faults. Contact 5 is grounded to flash diagnostic codes for inactive faults. Contact 3 is used in order to clear the diagnostic codes for all inactive faults from the ECM. Connector contact 2 is ground.Normal ModeWhen voltage is applied to the ECM and the machine identification plug is installed, the ECM flashes the machine code on the diagnostic code indicator. After flashing the machine code, the ECM enters normal mode and the diagnostic indicator is turned OFF. If a diagnostic code is detected, the diagnostic code indicator remains in the ON position.Normal Mode is used during normal machine operation. In normal mode, the ECM continuously checks for faults in the electronic control system. When a diagnostic code is detected, the diagnostic indicator is turned ON. See Service Mode.Service ModeThe ECM detects diagnostic codes that occur in switches, sensors, solenoids and the related harness circuits. A diagnostic code is detected when the signal at the control connector is outside a valid range. The ECM records the diagnostic code.If the diagnostic code indicator is ON and the diagnostic code indicator is in normal mode, diagnostic information is available in service mode. The service mode allows service personnel to see diagnostic codes that are detected by the ECM. The service mode allows service personnel to clear the diagnostic codes that are detected by the ECM.To enter service mode, disconnect the machine identification plug from the harness code connector. When in service mode, the diagnostics of the ECM are available to assist with the troubleshooting of diagnostic codes that are detected. The detected diagnostic codes are shown by flashing a diagnostic code on the diagnostic code indicator. This code is a two-digit representation of normal Caterpillar service codes. The codes consist of two three digit codes (CID and FMI) that are used to specify each detected fault. Each code that is flashed corresponds to specific identifiers. The identifiers are listed below:Component Identifier (CID) - The CID indicates the component that is faulty. The engine speed sensor or the transmission speed sensor are examples. The CID is a three digit code.Failure Mode Identifier (FMI) - The FMI tells the type of failure that has occurred. Examples that are seen are listed: voltage above normal, current below normal and abnormal frequency. The FMI is a two-digit code.Note: The diagnostic code that is flashed on the diagnostic indicator must be converted to a CID and to an FMI. In order to make the conversion, use the Troubleshooting, "Diagnostic Code List".The diagnostic code for the first available active fault is shown upon entering the service mode. The diagnostic code that is shown is on hold. When a diagnostic code is on hold, the code is shown continuously. The diagnostic indicator continuously flashes the diagnostic code for this active diagnostic code. This is maintained as long as connector contacts 1 and 5 remain open.Scrolling through the diagnostic codes shows all of the codes that are active one at a time. The connector contact for grounding 1 causes the diagnostic codes to scroll while in service mode. In order to stop the scrolling, remove ground from contact 1 when the desired diagnostic code is shown. The diagnostic code that is shown is now on hold. A diagnostic code of "11" indicates that there are no active faults.In order to cause the diagnostic codes to scroll, ground connector contact 5. In order to stop the scrolling, remove the ground from contact 5 when the desired diagnostic code is shown. The diagnostic code that is shown is now on hold. A diagnostic code of "12" indicates that there are no diagnostic codes that are inactive.Clearing a diagnostic code removes the diagnostic code from the memory of the ECM. When a diagnostic code is corrected, it is necessary to remove the diagnostic code from the memory of the ECM. Connector contact 3 must be grounded in order to remove a diagnostic code from the memory of the ECM when the diagnostic code for an inactive diagnostic code is on hold. After the diagnostic code is cleared, the diagnostic indicator is turned OFF. This indicates that the diagnostic code is erased. Scroll through the diagnostic codes that are active in order to remove the diagnostic code indicator from the OFF position. Scroll through the diagnostic codes that are inactive in order to remove the diagnostic code indicator from the OFF position. The ECM does not allow active diagnostic codes to be cleared.The ECM leaves service mode when the machine identification plug is connected to the harness code connector.Diagnostic ExampleThe diagnostic indicator is ON.Diagnostic code "31" is flashed - Use Troubleshooting, "Diagnostic Code List" in order to determine the numbers of the CID and of the FMI that correspond to a code of "31".CID 0641 - CID 0641 means that the diagnostic code is in the circuit for the forward solenoid .FMI 05 - Failure mode identifier 05 means that there is an open in the circuit concerning CID 641. See if a code is present and we can work on troubleshooting any issues you find.Use the diagnostic code indicator or a service tool in order to determine the diagnostic codes of the transmission electronic control. After determining the diagnostic codes, go to the proper procedure. Perform the procedure that corresponds to the given diagnostic code. Table 1Conversion of Diagnostic Codes Code CID FMI Description 11 No Active Faults N/A 12 No INACTIVE Faults N/A 14 N/A 928G 15 N/A 924G 16 N/A IT28G 17 N/A IT24F 18 N/A 938G 19 N/A IT38G 31 0641 05 Open Circuit in Forward High Solenoid 32 0642 05 Open Circuit in Reverse Solenoid 33 0643 05 Open Circuit in Forward Low Solenoid 34 0644 05 Open Circuit in Transmission Speed Solenoid 1 35 0645 05 Open Circuit in Transmission Speed Solenoid 2 36 0646 05 Open Circuit in Transmission Speed Solenoid 3 37 0346 05 Open Circuit in Ride Control Relay 38 0683 05 Open Circuit in Parking Brake Alarm 39 0421 05 Open Circuit in Load Check Relay 41 0641 06 Short to Ground in Forward High Solenoid 42 0642 06 Short to Ground in Reverse Solenoid 43 0643 06 Short to Ground in Forward Low Solenoid 44 0644 06 Short to Ground in Transmission Speed Solenoid 1 45 0645 06 Short to Ground in Transmission Speed Solenoid 2 46 0646 06 Short to Ground in Transmission Speed Solenoid 3 47 0346 06 Short to Ground in Ride Control Relay 48 0683 06 Short to Ground in Parking Brake Alarm 49 0421 06 Short to Ground in Load Check Relay 51 0641 03 Short to Battery in Forward High Solenoid 52 0642 03 Short to Battery in Reverse Solenoid 53 0643 03 Short to Battery in Forward Low Solenoid 54 0644 03 Short to Battery in Transmission Speed Solenoid 1 55 0645 03 Short to Battery in Transmission Speed Solenoid 2 56 0646 03 Short to Battery in Transmission Speed Solenoid 3 57 0346 03 Short to Battery in Ride Control Relay 58 0683 03 Short to Battery in Parking Brake Alarm 59 0421 03 Short to Battery in Load Check Relay 61 0190 08 Engine Speed Sensor 62 0191 08 Transmission Speed Sensor 63 0668 02 Invalid Input to Shift Lever Assembly 64 0168 00 Battery Voltage Above Normal 65 0168 01 Battery Voltage Below Normal 66 0650 02 Invalid Harness Code Input 67 0687 02 Invalid Option Code Input 68 0367 02 Invalid Input to Ride Control Switch 69 0621 02 Invalid Downshift Switch 71 0143 02 Invalid Neutralizing Function Table 2Detected Diagnostic Code See the troubleshooting procedure with the same CID and with the same FMI. CID and FMI Description CID 0143 Neutralizer Function FMI 02 Invalid operation of neutralizer function CID 168 Electrical System FMI 00 System voltage above normal FMI 01 System voltage below normal CID 0190 Engine Speed Sensor FMI 08 Incorrect signal CID 0191 Transmission Speed Sensor FMI 08 Incorrect signal CID 0346 Ride Control Relay FMI 03 Short to +battery FMI 05 Open circuit FMI 06 Short to ground CID 0367 Ride Control Switch FMI 02 Incorrect signal CID 0421 Load Check Relay (1) FMI 03 Short to +battery FMI 05 Open Circuit FMI 06 Short to ground CID 0621 Downshift Switch FMI 02 Incorrect signal CID 0641 Forward High Solenoid FMI 03 Short to +battery FMI 05 Open circuit FMI 06 Short to ground CID 0642 Reverse Solenoid FMI 03 Short to +battery FMI 05 Open circuit FMI 06 Short to ground CID 0643 Forward Low Solenoid FMI 03 Short to +battery FMI 05 Open circuit FMI 06 Short to ground CID 0644 Transmission Speed Solenoid 1 FMI 03 Short to +battery FMI 05 Open circuit FMI 06 Short to ground CID 0645 Transmission Speed Solenoid 2 FMI 03 Short to +battery FMI 05 Open circuit FMI 06 Short to ground CID 0646 Transmission Speed Solenoid 3 FMI 03 Short to +battery FMI 05 Open circuit FMI 06 Short to ground CID 0650 Harness Code FMI 02 Invalid code CID 0668 Shift Lever FMI 02 Invalid shift lever input line CID 0683 Parking Brake Alarm FMI 03 Short to +battery FMI 05 Open circuit FMI 06 Short to ground CID 0687 Option Code FMI 02 Invalid option code input ( 1 )924G, 928G and IT28G only
Customer: replied 1 year ago.
Hello again, I did everything you told me to do as far as parking brake switch, neutralizer switch, and auto shift. I only have a direction lever for forward and reverse and I am starting the machine in neutral with the parking brake on. I am starting the machine, applying the foot brake, releasing the parking brake, and putting it in gear. Today I tried to run the lift at least 5 times throughout the day and it will not move. It seems whatever is wrong has progressed to a point that it may not move again until it is fixed. I feel that might be a good thing because it is hard to find a problem that is so intermittent. I did remove the side panels today and I believe I found the ECM box. It is an aluminum box bolted up to the underside of the cab floor, under the fuse box. It is a solid extruded aluminum box with 2 ends on it held on with 4 bolts with one large plug bolted to it with lots of wires. I can not find the flashing light or diagnostic code indicator. Is there a way you can send me a diagram. I looked in my parts manual to see if I could find where they are located. The picture in my parts manual kind of sucks but it looks like it is showing some sort of plug and a bulb outside the ECM box but I'm not seeing it on my machine. I do understand how the light would flash out the code but I'm just not seeing the diagnostic code indicator. Do I have to open the ECM box? I have a friend that is a lot more mechanically inclined than I am. He said he would give me a hand this weekend. If you can send me some more info maybe he can figure it out if I can't. Thanks, Mike.
Expert:  catmastertech replied 1 year ago.
Yes, that is the ECM. Do not open the box, it does not have any repairable parts inside and you will only cause moisture to enter and damage the components.The lamp may be tied up in the harness just forward of the ECM. It should be near the large gray plug that is used for connecting a laptop and CAT ET software. You can use water to wash out the area, just don't put a high pressure was closer than 12 inches from the wires and connectors. This will force moisture into the connections and create a corrosion problem. The instructions I sent you cover about everything. If you have a specific item you are looking for, I will try to send you a picture. The only picture available is not of the lamp, only the area location. The lamp is small and can look like a fuse holder or connector end.

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