EVO steering circuit short, code 16

james5275

Registered User
Good morning everyone,
My buddies 89 started flashing the firm ride light the other day, code 16. According to the 35th tbird registry its a short in the EVO circuit. Any idea where we should start looking? The problem is ofcourse intermittant, when it does occur the car makes a sudden pull to the right (which isnt to cool at 100+mph). He came close to killing himself, but hey, not a scratch on the car! I did a search and found only 1 thread with the same problem, but the originator didnt reply with a fix. Thanks for the help, JJ
 
I'm sure that its a problem with the EVO. When the problem occurs, I can feel the pressure difference in the steering. We checked all the actuators last night, all good. When switched between firm and auto, I can feel the difference in the ride, like it should. Remember, the EVO, ARC, TPS, Speed sensor, etc. are all linked together. How the heck do I add a link to my post?
 
Glad you made this post as I've encountered similar problems. I've had long term problem with my ARC. Actuators are fine, found short in circuit board behind where the FIRM light indicator is located.
Changed out circuit board, but still having problems. ARC feels as is if it works ok, but upon start up I often get quick series of clicks from rear actuators. Replaced soft relays and changed out ARC computer, still no joy.

Lately, I get a scary pull in my steering wheel. Feels like a gremlin is figthing the steering wheel or I get an unpredictable "spike" in the steering. This condition is usually felt while engaged in a long but somewhat sharp turn, like on a exit ramp.
I'm believing my EVO is culprit. I'm in middle of replacing p/s pump and EVO. Hopefully, this will cure at least the steering problem.
 
Please let me know what happens. Yes, his car is doing exactally what you described, pulling to the right. One hell of a safety issue. Have you tried pulling the connector on the valve (on the pump)? This would leave the system in high pressure all the time but should at least stop the gremlin. I did that once after some p/s maintenance on my 90 (forgot to plug in the connector) and the car is VERY touchy at high speeds.


Anyone else have some input? I think this is a pretty important issue. When the system let go, he had no warning and luckily no other cars were around. It took him 2 1/2 lanes to catch his bird. NOTE, he was traveling 100+ mph, I felt it at 75 mph on a test drive and thank god I was expecting it. JJ
 
remove inspect EVO valve

After some more searching on sccoa, it looks like a lot of us have had this same problem, and most have learned to deal with it. No one has mentioned dissambling/inspecting the valve so I'll give it a shot. Hopefully it isn't too difficult, I'm sure it works just like a solenoid. I'll post my results. JJ
 
ARC code 16 FIX!!!!

After 3 hours of trouble shooting, I'm pretty sure we found the problem. Didn't end up pulling the EVO out. We removed all the shrink wrap and inspected all the wires to the EVO. For those that didn't know, there are 2 connectors in that loom, one at the EVO and another connector about 8" up the line. We dissassembled BOTH connectors and tightened all the metal terminals. Now the system works like a champ. HHHOOOOYYYAAAA!!!!!! I am 100% sure there are no broken wires in the system, we checked them with a meter. Test drove the car for about 2 hours without a glitch, except loosing to a SALEEN MUSTANG (deatils in the racing/track forums) ps, anybody have a spare WHIPPLE they want to get rid of? lol.


Everyone let me know what you think of our fix, or possibly the system just decided to act normal again. Someone give it a try and let me know what happens. JJ & AL
 
Just a couple points.

#1 - If this problem is happening to someone and they don't know how to fix it, they can disable the EVO by simply disconnecting the wires to the valve at the power steering pump. You'll end up with full boost in all situations so It'll fell weird initially. But at least then it isn't changing back and forth in the middle of a turn.

#2 - The steering wheel isn't pulling anything. The driver is pulling the steering wheel. Likely the driver is driving with only one hand on the steering wheel and relying on the natural tendancy of the wheel to self center to offset the force of their hand. When the EVO valve "fails" it fails "safe". In this case it means it stops creating higher resistance in the power steering system. So once the steering pressure comes back, the person with just one hand on the wheel causes the steering wheel to move easier, and the weight of their hand to pull the wheel to whatever side their hand is on the wheel.

I'm glad you were able to track it down to a poor quality connection. That gives others hope.
 
Are you saying that when the system fails, its the drivers bad habits causing the car to pull? Sorry, I have to disagree but I understand what you are saying. I was in a left turn when it first happened to me, pulling to the right. And that situation right there would eliminate the possibility of your theory. Anyway, its a really freaky deal, and I hope we fixed it. JJ
 
When the rack goes bad you can get a hydrolock in the system. Had this problem on a 90 SC. Seemed to happen on left turns. You would come off the highway take the ramp and be at the stop sign. Merge left and then the car wouldn't straighten even though I pulled hard right, then it would release and be fine. Bought a complete rack assembly from ORielly Auto Parts for around $90 and it included inner tie rods. I think the EVO can only do high boost and low boost. I don't think it's varible. The rack has a built in varible ratio though. Going up ramps and accelerating causes the steering boost to vary. I think it's a combination of the ratio built into the rack and the EVO changing from high to low boost setting. There is a certain speed tha to force the EVO to low boost. I beleive that large steering wheel angles force the EVo back to high boost. So you get a situation where things feel funny sometimes. It shouldn't feel dangerous though. Just unplug the EVO connector on the pump and leave it in high boost mode to test to see if your problem goes away.

Jerry
 
I'm not qualifying the habits. I'm simply stating how the described action could occur related to a failure of the EVO valve. When sudden things like that occur, it's often difficult for a person to qualify what really happened.

The EVO valve is not able to influence the direction of the steering. It's location allows it to only affect the flow rate of the hydraulic fluid through the system and thus the perceived assist.

If you feel that the steering actually worked to change the direction of your input, then the problem would need to be in the rack or the mechanicals of the steering, not with the hydraulic assist.

The EVO valve has a orrifice that is variable in size. It is not as simple as open and closed. It takes an electrical input to restrict hydraulic flow which is done through a proportional controller that is driven by the Automatic Suspension controller. The inputs come from vehicle speed and the steering wheel angle sensor.

Due to such a sudden change in assist, it certainly isn't a problem someone should live with for long. It can really suprise someone. It would be better if someone things the EVO valve is acting up that they disconnect the valve and live with the higher assist for a while.
 
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