Just bought a used 299d XHP with 1900 hrs. has code for LH speed sensor #1, and LH #2 frequency or pulse. At Idle RH reads 0-RPM, LH reads like 16900 RPM. I pulled the sensor and it looks good, one very small nick on the edge. All wires look good. Second problem which may be related.. Charging system has new battery, Had alternator checked-it's good. Battery reads 12.9 volts and passes a draw test. At idle the machine will increase RPM to adjust for battery voltage and charge at 15 volts, even though the battery voltage stays above 12.4 volts I know there's some great experience out there, Any Ideas or solutions? Thanks, KW
I will start with problem #2. Are you sure it is going into an elevated idle because of the charging system? I would suspect it is actually idling up to perform a passive regen due to this machine being a Tier 4 machine. These machines will do that based on soot level, which you can only see with Cat ET and not in your monitor. Problem 1. Without a schematic currently at hand I cannot tell you what ecm pin locations your wires to the sensor go to. I would however check the connector from the sensor on the undercarriage frame are. They are known to come apart underneath the sheath protection, if that machine even has the sheathing on. Lift the cab also and verify that the wiring is not rubbed under the cab either. If I had to take a shot in the dark I would actually guess your sensor has failed, I have seen a ton of sensor failures. Could swap sensors from left to right and see if your problem follows the sensor or the location.. Best of luck.
Thanks for the input. Problem 2, readout says idle increased due to low voltage. I will try the switch of sensors and see where that takes me. All wires are sheathed and look good under the cab. I will post the progress
Switched the wires from RH to LH at the harness Lower end under cab. Still says LH speed sensor #1 and LH Sensor #2 . so that didn't change anything, which should indicate a connection problem in the upper portion of the harness. Cannon find sensor #2 so that could be the problem also. Any idea where that is located?
That sensor is actually a dual pickup sensor. Both sensors are in the same body. You will only have one physical sensor. Do you have a serial number? I can look at a schematic and tell you more then.
cat 299d XHP ser # CAT0299DEJST00562
When I pulled the sensor, the portion that was inside the motor was wet with hydraulic oil. Is that normal?
Yes thats totally normal, oil will drain out
I have not found any bad or loose connectors. No chaffed or worn wires. I put Dielectric grease on connectors. No change At Idle, RH sensor reads 0 RPM, LH sensor reads over 16000 RPM with fault code for signal frequency or pulse. switching wires from RH to LH should have moved the fault from L to R, but had no effect. Not sure where else to look.
Heres what you need to do. If you tip the cab up you'll see the machine ECM on the back (It would be behind where the back of the seat is but under the cab), there are 2 big square connectors on the ECM. One is "J1" and the other is "J2", youll see the J1 and J2 cast into the ECM next to each connector so you can tell which is which. You need to get a multimeter and Ohm out the wires going to the ECM connector from the speed sensor. This will tell you for sure if your problem is related to the wiring or if it is the sensor itself. Ill attach an image for the wiring from the sensor to the ECM. If you have continuity in each wire then your sensor is junk. If you get OL or no continuity then youre problem is in the wiring or a connector. Its not totally uncommon for 1 wire to fail inside the loom. Sometimes pin sockets can look okay but can get wore out to the point where they no longer or just barely make a connection. So once your meter is hooked up, try to wiggle things around to see if you can make a connection. If you can, then you have just isolated your problem. I hope this helps
Also.. keep in mind on these. The machine ecm MUST receive a valid frequency from from the speed sensor in order for the code to become inactive. So you need to start the machine and move it after you think youve fixed something. Even if you fix the problem, if all youre doing is turning the key to the on position, youll still have an active fault code until you move it.
Those Cat tracked skid steers are notorious for chaffing hoses/wiring where they run through the frame. Usually right on that black guard. Sometimes they'll chaff up without cutting through the kevlar covering.
I had the same problem. I was told that the sensor often fails last in the series of events. I forget my code but it was abnormal pulse width or frequency. I spoke with the CAT heavy machine manager in New Mexico and he said the connector between the two wires leading to the sensor is more often the problem. It worked for me for a xouple months....until, of course my sensor actually did go out :/ I asked him to explain it since it makes no logical sense but and all he could say is that it is what it is. The wires are all the same part number so maybe try to take one of the new ones you got (put the old one back on) and use it between the two.