SaabCentral Forums banner

1 - 17 of 17 Posts

·
Registered
Joined
·
487 Posts
Discussion Starter #1
Hi not sure if any of you have followed this issue on my YouTube or other forums but having a nightmare with my 900 turbo convertible from 1992. The issue started with the the Antilock light coming on intermittently and then soon it was accompanied by a slight clicking from the pedal when i braked hard. A friend did and ISAT test and got a code 1222 but when he was doing the test the brake pedal went solid and then had no brakes at all unless I broke hard - then the Antilock light and brake fluid were permanently on - I was advised to change the pressure switch on the abs pump which didn't change anything.

no fuses have blown and the relay has been tested working - also changed out the ABS ECU and still no change - have now changed out the pump, pressure switch and accumulator. When refitted with tested working parts still the pump does not come on off the ignition - I tested the pump manually and it will not pressure the system - the brake fluid level doesn't move when the pump is functioning. I'm now stuck ! Have no clue what is going on - any help is greatly appreciated
Thanks
Troy
 

·
Registered
Joined
·
8,446 Posts
How old brake fluid you have in system?
 

·
Registered
Joined
·
487 Posts
Discussion Starter #3
The whole system has been bled and changed recently
 

·
Registered
Joined
·
158 Posts
How old are the flexible lines? I've seen old ones swell internally and act as restrictors or even one-way valves, holding pressure at the caliper, despite looking fine on the outside.

What about the master cylinder? Are you sure it's doing it's job correctly?
 

·
Registered
Joined
·
60 Posts
Look around under the seat near the control module. I think there is a single wire connector that if it gets unplugged you basically have no brakes. I think it is located in about the center of the car towards the seat back.
 

·
Registered
Joined
·
6,782 Posts
The hydraulic part of the brake system is self contained - basically power from the battery runs through a pressure switch and when the pressure switch is open (high pressure) the pump stops, and when the pressure switch is closed (low pressure) the pump runs. The accumulator stores pressure. There is nothing more to it than that. You can run the car with essentially only power and ground to the hydraulic unit.

The ABS part is the ECM getting feedback from the wheel sensors and controlling the valve body. When there is a speed differential between two sensors the ECM cycles the valve body to bleed off pressure to the slower wheel until the speed equalizes.

You need to determine where the issue is - whether the hydraulic unit cannot make or store pressure, or whether the ECM cannot read wheel speeds it is improperly controlling the valve body.

I think my first shot would be to verify reliable power to the hydraulic unit and the disconnect the ECM and valve body and see whether the system behaves properly. That should isolate the issue so that you can take the next step.
 

·
Registered
Joined
·
487 Posts
Discussion Starter #7
Ok thanks for the input - I will get to it and see where we're at
 

·
Registered
Joined
·
487 Posts
Discussion Starter #8
When it comes to electrics I'm lost - can I have the idiot guide to how I verify power to the hydraulic unit? As I said when I power the abs pump manually direct off the battery it doesn't pressure anything and the brake fluid level doesn't change so I'm thinking the first thinks to get working would be that when the pump fires it does it's job.
 

·
Registered
Joined
·
6,782 Posts
The concept is that the pressure switch on the ABS unit sends an "on" signal to the ECM, which grounds #85 on the pump relay. When that happens, the pump runs. Once the pressure switch sees the requisite 2600psi, the ECM cuts the ground and the pump stops. You can run the pump manually by either grounding #85 on the pump relay, or by jumping 30->87 on the pump relay. Doing either of these will bypass the pressure switch, so you don't want to leave it running. But you can verify the pump runs. To know more than that, you need a pressure gauge that can read 2600psi. By the same token, the goal here is to verify the pressure switch is doing what it should - telling the ABS ECM to start and stop the pump. I think you should be able to verify that function by removing the pump relay, pressing the brake pedal a dozen times to relieve pressure, then verifying there is ground at #85 of the pump relay. If there isn't, either the ABS ECM isn't doing it's job, the pressure switch isn't doing it's job, or there is a wiring problem.
 

·
Registered
Joined
·
2,800 Posts
I dont really participate in the 900, but i think i saw ur video.

Brake is something and ABS is something else.

Code 1222 is main valve which usually means bad ECU, connect a test light to ground, With ignition ON, test both pins at the main valve connector, then switch test light to battery positive and test both pins again, report results.

Brake lamp only lights if low fluid level sensed or low pressure.
At the pressure switch connector, jump the blue and the black wires, does the pump run ?
 

·
Registered
Joined
·
2,800 Posts
I know, this will split the circuit into two halfs, control side or actuation side .
If pump runs, then i dont have to worry about the actuation side, and next will test the control side, which is only the fluid level sensor and the pressure switch . Dont u agree
 

·
Registered
Joined
·
487 Posts
Discussion Starter #13
Ok the first thing I need to do is get pressure back into the brake system - I had to remove the whole abs hydraulic unit to change the pump so I drained the brake fluid reservoir - now I have put everything back together topped up the reservoir but now the pedal just goes to the floor and I have no brakes at all ? So I assumed running the pump manually would pressurise the system but the brake fluid level doesn't move. So I guess the first thing to do would be to get some kind of braking back regardless of the abs system right ?
 

·
Registered
Joined
·
2,800 Posts
The ABS is just a function of the braking system, wether it has a fault or not it should not effect normal braking, u can remove the ABS module totally and the car would still brake as normal car.

The braking system however, is divided into two halfs, front brakes and rear brakes.
Front brakes are just normal assisted brakes, losing electronics should not prevent them from working, rear brakes however are 100% assisted brakes, which mean they wont work without the pump building pressures and the accumulator storing that pressure.

Now to make sure u start fresh, start with bleeding the front brakes (with the ignition OFF) and not to complicate things, just make it gravity bleeding, so open each bleeder individually, and wait until fluid come out by itself, when the fluid start to flow, give it like 2 minutes and then close the bleeder, repeat on the other side .
This should restore normal brakes on the front.
Report back .
 

·
Registered
Joined
·
6,782 Posts
I know, this will split the circuit into two halfs, control side or actuation side .
If pump runs, then i dont have to worry about the actuation side, and next will test the control side, which is only the fluid level sensor and the pressure switch . Dont u agree
Yeah, totally. I believe this is exactly the right approach!
 

·
Registered
Joined
·
487 Posts
Discussion Starter #16
Ok thanks for the advice - I have a plan now how to go forward . I appreciate the support ! As soon as I can get to it I'll report results
Thanks again
 

·
Registered
Joined
·
36 Posts
Hi not sure if any of you have followed this issue on my YouTube or other forums but having a nightmare with my 900 turbo convertible from 1992. The issue started with the the Antilock light coming on intermittently and then soon it was accompanied by a slight clicking from the pedal when i braked hard. A friend did and ISAT test and got a code 1222 but when he was doing the test the brake pedal went solid and then had no brakes at all unless I broke hard - then the Antilock light and brake fluid were permanently on - I was advised to change the pressure switch on the abs pump which didn't change anything.

no fuses have blown and the relay has been tested working - also changed out the ABS ECU and still no change - have now changed out the pump, pressure switch and accumulator. When refitted with tested working parts still the pump does not come on off the ignition - I tested the pump manually and it will not pressure the system - the brake fluid level doesn't move when the pump is functioning. I'm now stuck ! Have no clue what is going on - any help is greatly appreciated
Thanks
Troy
The only problem with my brakes that ever really threw me was when the diode from the electrics blew for some reason. This obscure part lives under the ABS fusebox on my 93 900s, and likely on your car, as well. The symptom was a rock-hard pedal with no feel whatsoever. Fortunately, it was when there were still SAAB dealers and I was able to obtain a replacement. Man! Have you ever tried soldering something out in the open, in windy, sub-freezing weather; getting frostbite in your fingers while worrying about if the heatsink will be okay; with a feeble, marginally-hot soldering iron? Hope that I never have to do that again!
 
1 - 17 of 17 Posts
Top