LX470 High Oil Pressure on Gauge

Joined
Apr 15, 2022
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I have had the truck for a year, and have learned a lot from this forum. I am stumped on my current issue.

99 LX470

Starting a few days ago, when starting the truck, the oil pressure gauge goes straight to mid-range, then steadily climbs until it is pegged on high.

I changed the sending unit, same issue. I put the old one back on.
I hooked up a mechanical gauge, it was at 80 psi idling.
Thought that my filter was clogged, so I changed the oil and filter. Only a few thousand miles since a change, but stranger things have happened.
After the oil and filter, pressure went up to 70 psi, then dropped to about 40 psi at idle after it warmed up. I thought I had fixed it.
Put the old sending unit on and plugged everything up.
Same issue. Pegging on high.
Drove it around, stopped at the car wash. When leaving, it acted right. I thought it had to relearn something after being unplugged.
After pulling away, when RPM went up a little, the gauge started climbing and never went back down.
Now, every 3-5 times I switch it off and start it back up, the gauge acts correctly at idle.
When I give it a little throttle and the gauge climbs, it climbs until it pegs on high.

I don't think Techstream gives an oil pressure reading, but I'll plug it in and verify.

I don't think I have a real oil pressue issue because the mechanical gauge gave good readings, and it acts right some of the time.

I think the sending unit is okay. The old one looks new, and I had the same issue when I replaced it, although I didn't leave the new one on very long.

I feel like it must be the gauge.

Has anyone seen this before, or have any ideas on how to troubleshoot?

Thanks in advance for the help.
 
Joined
Jan 11, 2011
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the stepper motors are known for going out on these gauge clusters. My fuel gauge has a mind of its own. there is a company that repairs them , but the cost is (at least in my case) like $700. so I just live wth it
 
Joined
Feb 27, 2022
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FWTX
In your case, seems to be the cluster. I have the same.
 
Joined
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Thanks for the input. I found a parted out LX and was able to get a cluster for $100. It will be here in a few days, and hopefully that will do it.
 
Joined
Sep 2, 2010
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Sarasota, Florida
I've been contemplating hooking up a mechanical guage full time. Would you mind shareing a pic of where you attached it and what fitting is needed?
Thanks.
 
Joined
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Now it's from bad to worse. I bought a used LX cluster from Facebook marketplace to test with. I can't remember the year. I know some models are different, but I'm just trying to test the oil pressure, so I plugged it in. Good news - the oil pressure was correct, so I have a bad stepper motor. Bad news - the thing lit up like a Christmas tree. ABS, Brake light, whatever else. So I took it out, put in my old one, and will order a stepper, or maybe 6 and do them all. I had a heck of a time plugging it back in. Couldn't get the connectors on the back to line up. Finally got it.

But - the battery light came on, stayed on for a minute or so, then went off. No biggie, I thought it had to re-learn something. But then it came back on to stay. The voltage on the gauge is good.
And - there is no AHC light on the cluster that would normally indicate Neutral, and the up and down does nothing.

I figured I popped a fuse with my stupidity. Checked every AHC fuse and the Gauge fuse and they're all good. The only thing I know to do next is take the negative off of the battery in hopes that something resets. Then when my stepper comes in, take it back out, change the stepper, make sure the connector pins are straight, and take care to get the connectors properly together. I may try to make a tool or somehow figure out how to apply proper force to seat them.

Is it possible to not get the connectors seated properly? I tightened up the screws but wonder if that's good enough. Is there a trick to getting them back in? The dude on the Youtube video I watched said he put his left hand behind the cluster and pushed them in. I don't see how in the world he could do that. I can't get my fingers a few inches in. I tried it with the connectors clipped into the rear holes, but ultimately had to pitch the rear ones up a little bit to get things to align, then pushed the cluster in.

Someone give me some direction and advice. What would make my battery light and AHC go wonky after taking the cluster in and out?

Thanks in advance for your help.
 
Joined
Sep 2, 2010
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Sarasota, Florida
Did you tighten the lower screws; i think the screws pull the plugs together?
 
Joined
Apr 15, 2022
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USA
Sorry to go on and on, but I hate when I see these forum posts with a similar problem as mine that end up in a cliffhanger. I started at the beginning, and the alternator is not putting out any voltage. Apparently, my alternator died in the few minutes after I was messing with the cluster. 11.96v not running. 10.86v when running. Next step is an alternator. Then I'll work on the AHC if the alternator is not somehow the culprit there as well.
 
Joined
Apr 15, 2022
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As my saga continues, I need some additional help. Changed the alternator, fixed that issue. Didn't have to remove the radiator or radiator hose, I was able to wiggle it out the bottom, so it only took an hour or so.
Now the AHC works, but there are no H, N, L lights indicated on the cluster. Has anyone ever seen this issue? I have found threads that address AHC not working, but nothing about AHC working with no lights.
 
Joined
Mar 19, 2017
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As my saga continues, I need some additional help. Changed the alternator, fixed that issue. Didn't have to remove the radiator or radiator hose, I was able to wiggle it out the bottom, so it only took an hour or so.
Now the AHC works, but there are no H, N, L lights indicated on the cluster. Has anyone ever seen this issue? I have found threads that address AHC not working, but nothing about AHC working with no lights.
Make sure AHC ecu is plugged in. Maybe failed at the cluster?
 
Joined
Apr 15, 2022
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I was convinced that the oil pressure issue was a bad stepper motor (gauge), so I took the one from my donor cluster and switched it out. I switched out the burned out D light while I was there. I was also convinced that the AHC light issue was due a bad cluster installation. Good news, bad news - I re-installed the cluster and had the same issue with the oil pressure, but the AHC lights worked properly. I took great care to get everything seated properly, so that was the issue with that.

I learned during this time that the oil pressure port is a 1/8 bspt, so I ordered a tee that is 1/8 bspt x 1/8 npt out the side, bought a mechanical gauge, and mounted it under the hood. Nothing like some old fashioned psig for a sanity check.

At this point, the oil pressure is good, the sending unit is good, the gauge is good, it must be a broken wire.

I traced the wire (yellow with a green stripe) up to the front of the engine. Cut the wire, put in a jumper, and BAM!

I then used proper connectors, taped them up, and zip tied the wire to keep it away from the serpentine belt.

I spent a lot of time troubleshooting, and should have thought about the wire before I dug so deep. I recently changed the steering rack, so I broke the wire doing that. Live and learn.

If your oil pressure pegs, it's a broken wire.

Yellow wire with green stripe.
IMG_8709.jpg


My jumper wire with an alligator clip.
IMG_8710.jpg


My tee setup for the mechanical gauge and the sending unit.

IMG_8713.jpg


I mounted the mechanical gauge using an existing ground screw on the driver's side fender. I just mounted it with one screw. Even though I solved the issue, I'm leaving the mechanical gauge. It doesn't hurt anything.
IMG_8711.jpg


During all of this, I started getting an airbag light with a B0101 code. I have my new clock spring on the way, then I'll be good to go. Hopefully.
 

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