Working on a d6m today Ser#3wn01441 Brakes won’t release If anyone could help would be great
Got any Active Codes (SERV CODE icon illuminated) on the Monitor Panel.?
113 0691.07 113 0692.07
Incorrect speed signal when a clutch is engaged for the REV clutch and the FWD clutch. Here are the troubleshooting procedures for both. Does the parking brake light go off when the switch is moved to the OFF position.?
Yes the light goes off and on with the switch And the solenoids energize with the switch
OK, so before getting into the troubleshooting procedures...... Is the transmission oil dark in colour and/or does it smell burned.? Has the oil been drained since the problem started.?
No oil is supper clean
Try the troubleshooting procedures then and see where they get you. If you want a complete electrical schematic for the machine please ask.
There’s only 4.5 volts between the white and green wire At the reverse modulation valve No change in power when we shift the gear switch
And I do have the wiring schematic
You're getting way ahead of yourself. There are a lot of pressure checks to be done before you go near it with a multimeter, and when you do you will actually be measuring current flow through the solenoid coil. Refer to the troublehsooting procedures.
420 psi at the port for the modulating valve
380 at the priority valve
There are four ports on the brake valve with zero pressure
It might be a stupid question but have you checked the state of the brake pedal switch.? That switch is normally open and only closes when the brake pedal is almost at the bottom of its travel. At that point when the change of state of the switch (battery voltage) is received by the Power Train ECM it command a dump of the parking brake pressure. You'll find the switch in Grid B-5 of the schematic, Page 8.
Park brake switch seams to work the mat it should
So the switch contacts close right at the bottom of the pedal travel.? If that is the case then it’s back to continuing the steps of the troubleshooting procedure for the -07 Diagnostic Codes.
We have found that there is only 4.5 volts going to the priority valve solenoid When the brake switch is of should there be more We are going to try a new brake switch to see if that could be the problem
It is really simple to test the service brake pedal switch - just simply unplug it. The only purpose it serves is to apply the park brake when the service brake pedal is pressed right to the floor.
I think the op is missing something in the translation. Nige is talking about the secondary brake switch in the brake pedal on the floor and the op is still hung up on the park brake switch.
I was thinking that as well, but apparently he has an electrical schematic - it shouldn't be hard to figure it out when I posted a snip from the schematic on the previous page showing the secondary brake switch and the brake pedal rotary position sensor. What has me thinking elsewhere is that according to the OP the Park Brake light goes off when the switch is moved and also there are no Codes for the PB switch. On the basis of the information supplied that implies that the PB switch is working fine. HOWEVER......... the service brake switch will cause the PB to apply when the contacts are closed. That is a system working exactly as designed and would not in normal circumstances create a Diagnostic Code.
To eliminate any confusion this is the switch I'm talking about. #39 hidden up in the circled area behind the service brake pedal.
We have replaced the brake pedal rotary switch and the service brake switch seams to work properly The question I have now is about the priority Valve can you tell we what it does There is no oil pressures past this valve We have replaced the solenoid and the solenoid valve When we tested the wires they test good But when we test the voltage going there it only gets 4.5 volts when the the brake switch is off
Do you have, or have access to, Caterpillar ET.?
Attached the SysOp document for the Priority Valve.
Have you tried simply unplugging the electrical connector that is right next to the switch.? Yes, it will throw a Diagnostic Code if you press the service brake pedal right the way to the floor after you do it, but if you don't it should give you enough time to check that it isn't a weird input from that switch that is causing your problem.
That switch is working the way it should When the machine is running it throws no codes Until ten to fifteen seconds after you take the park brake off All new solenoids on the brake valves thay power on and off with the switch But there is not oil pressure getting to the brake valve
So since the last time I posted ive had a cat Machanic come in found a speed sensor wasn’t working put in a new one did not change a thing With the computer on it no problems exist all electrial work the way it should the problem is in the hydraulic system there’s is no pressure getting to the brakes he thinks that it is the priorty valve and wants to put a new one on and see if that works can you tell me if there’s a valve in the priority valve that dumps the oil back to the tank that could be broke or stuck open the p port at the back of the trans mission has the right pressure
Did he remove the existing one and open it up to inspect it/check it against specification.?
Yes all is good i see on the illustration there’s a small valve with a ball could that be stuck open and the flow is just going back to tank