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- #41
This pic was taken on level ground with truck running in N.
AHC help needed
- Thread starter Kalino_74
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- Thread starter
- #42
I started having problems with the front while running snow chains on the front tires during a bad snow storm. They weren’t hitting anything under the truck so I can’t see why it would have an effect but I figured it might be worth mentioning.
What’s the status of “main relay expectation” ? I’ve never seen (or more to the point noticed) it OFF before and I can’t help but think there maybe a relationship between it showing OFF and the 0.7in difference in front height sensor readings during your non test mode drive. The +.2/-.2 readings are good/ok for stationary readings. I’d try and get both of them closer to zero and then see what they are during a normal drive and if main relay expectation is ON when there’s less of a sensor value spread (and hopefully the dampening is good). If the front height is creeping up due to worn sensors or electrically noisy sensors (think a scratchy volume control on an old amp or stereo) then the increase in pressure degrades damping ~ 1in in height equates to 2.2MPa in front pressure. I’ve long thought that height sensor dynamic feedback could be the root of many undiagnosed AVS dampening issues. After all it and speed are the two critical inputs to the ECU for adaptive variable suspension.
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- #44
Paddo, I’m working on getting my height sensors in spec right now. I did notice when I move my steering wheel a quarter turn the angle number is really high. It shows right at 15 degrees when straight. Is this normal. I loading pics so you can see what I’m seeing.
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- #45
Nevermind the first pics these are correct ones.
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- #46
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- #47
Sorry I really screwed that up. Turning the left a 1/4 turn yields -103 degrees and a 1/4 turn to the right yields +79 degrees.
Sounds about right, that display isn’t degrees as generally understood, ie in 360 degrees in a circle, but a mystical electronic representation. If you do a lock to lock turn turn (about 3.4 full turns of the steering wheel) you’ll see that value change from +1100 to -1100s - or something similar. I don’t believe your problem lies with steering angle, I’m more interested in why your damper switch 1 data field is now blank and previously you had a blank main relay expectation field. I’ve never seen blank fields, seen offs and ons, strange numbers but not blanks. So now I’m thinking either the AHC ECU data is valid and the mVCI has random issues - the data protocol is old, simple, single line stuff similar to Rs-232- or the ECU or its interface is behaving randomly and the mVCI is reporting what it sees, albeit inaccurate incomplete data. It wouldn’t hurt to pull and reseat the 3 AHC ECU connectors, check and clean the signal grounds and operate your laptop off battery or mains (not a vehicle powered inverter) to ensure there is no floating signal to ground shenanigans going on.
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- #49
So I got the front height sensors within .1 of each other. I took for a ride and still firm. I decided to unplug the front two height sensors and took it for a drive and it drove pretty nice. Not as soft as the first few steps in the 16 active test mode but pretty nice. I can actually compress the dampers in the front by pushing down at each corner. I know the truck has had water come up to the bottom of the door seals during hurricane Harvey so I’m thinking about taking apart the front sensors and giving them a cleaning. Do you think that would be a good idea?
The main relay expectation and the damping force 1 not showing a value I think was just a blip. I had taken two photos within seconds of each other and the first photo showed the values correctly.
The main relay expectation and the damping force 1 not showing a value I think was just a blip. I had taken two photos within seconds of each other and the first photo showed the values correctly.
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- #50
I also noticed my neutral pressure changed by .6 with the sensors unplugged.
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- #51
They dropped by .6 I should have mentioned that.
You got it to raise from L to N with the sensors disconnected? Haven’t tried that one before
. The FSM actually calls for the fluid temperature sensor to be disconnected when taking rear pressure readings - some report that seemingly high rear pressures drop with the temp sensor disconnected, a few notice no difference (self included) and most don’t bother.- Thread starter
- #53
I was already in N when I disconnected the sensors and it stayed in N. Have you ever seen a bad pressure sensor? I’ve gotten a lot of pressure readings in the 2’s and 3’s mostly in the front but occasionally in the rear. Even after cycling from H to L then back to N I’ll still get some goofy readings. When checking the pressure with a gauge do you just hook up the tubing/gauge to the bleeder screw?
Pressures aren’t constantly monitored, they are just snap shots of the pump output at the time the respective solenoid switches so you can’t put any stock in them other then what’s reported during a L to N raise cycle. And even then it’s very easy to get spurious readings. Yes, the gauge just replaces a bleed screw, you do your L to N lift and read off actual system pressure with no guess work or second thoughts. After adjustments you then depressurize, remove the gauge and refit the bleeder. You could easily rig up a permanent arrangement too.
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- #55
I kept the front height sensor’s unplugged and the front isn’t as stiff. Whenever I plug them back in it intstamtly goes back to being stiff. It even leveled it self out in the front without the sensors being plugged in. I think I’m going to just drive it this way until I find out what’s wrong. I wish it would throw a code already to give me a sign. Ha!
Suspect you’ve got one or both height sensors sending bad feedback whilst in motion - extra uncompensated height = extra pressure = stiffer ride. Unplugging them isn’t a solution unfortunately, might be worth investing in a pair of Aisin replacements from rock auto for ~$310.
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- #57
I’m kinda thinking the same thing. Things pretty much went haywire after running snow chains in the front for a week. I’m thinking the excessive vibrations might have damaged them. I will give it a try and report back. Thanks again for your wisdom.
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- #58
Hi Paddo, I replaced the height sensors and I’m still having the same issue. I know you mentioned not to put to much thought into the erratic neuatral pressure readings but it’s really strange. While trying to get my front pressure correct I’ll get the front to around 6.1 and make tb adjustment then recheck the results and it will show for example Front 7.6 Rear 3.2 then I’ll run it again then it will show Front 2.8 Rear 7.2. At one point I got a C1762 and the pump made a loud sound but I cleared it with techstream and it hasn’t done it again. I just can’t figure out why it rides beautifully in the 16 step test and rides good when the front height sensors are unplugged?
I was wondering if you had any more thoughts?
I might try and rent a pressure gauge and check pressure at the actuators. You had mentioned installing permanent fittings in place of the bleeder screws. Where can I source these?
I was wondering if you had any more thoughts?
I might try and rent a pressure gauge and check pressure at the actuators. You had mentioned installing permanent fittings in place of the bleeder screws. Where can I source these?
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- #59
Paddo, I finally found the problem it was a bad AHC ECU. I ordered a used one off ebay for $90 and installed it last night. The crazy thing is I never had a trouble code for anything. My rig drives nice and smooth now. I'm going to recheck my pressures again later today and finally start enjoying the truck again. Thank you so much for all your help.
@PADDO In your experience have you encountered discrepancies between the step values reported in Techstream and the actual step control applied to the damping actuators? The comfort profiles (i.e. comfort, sport, etc) in the Techstream screenshots @Kalino_74 posted showed expected step values, while both stationary and during normal driving, however the actual control signal sent to the actuator seemed more aggressive (stiffer).
Tagging @uHu because you two know what's up.
