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  1. #1
    Bogger
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    Electrical and other gremlins (oil pressure, crank sensor, blower motor)

    So I'm having fun. We've been trying to sell our house and move to far north Utah but of course that hasn't happened yet. I was hoping to have moved by now so that I could park my truck for a bit and give it a good going over. But since that hasn't happened the Alpha has apparently decided to start voicing its displeasure and is starting to give me new grief.

    Last week it suddenly died while stopped at a light. Started up but was it was grouchy, drove it a few miles then pulled over and shut it off for 5 minutes or so. Started back up no problem and hasn't died since. The code it gave me when that happened was P0335 for the crankshaft sensor signal. I had that earlier this year when I had my previous set of gremlins that ultimately went away when I replaced the throttle pedal assembly (after also replacing the throttle body sensor).


    Next up a couple weeks ago I got a low oil pressure alarm while taking a slow but sharp turn. I have a separate MaxTow oil pressure gauge that feeds off the port above the oil filter (remember this is a 5.3L V8) but when I got the alarm it cleared before I could look at my MaxTow gauge so I wasn't sure if I really did lose pressure. I checked the oil level and it was only about a quart or so low, but I topped it off anyway. Didn't have any more issues until yesterday when I started regularly (but not consistently) getting oil pressure alarms while accelerating, usually from a light. However I have also gotten the alarm while cruising, so it's not dependent on acceleration. This time I have been able to verify with the MaxTow gauge that I do in fact have full oil pressure (my pressure range hot is 28psi or so at idle, and 35 to 50 psi while cruising/accelerating) when the alarm is going off. I also see with my Ultragauge that the computer is seeing either extremely low pressure (~1 psi) but majority of the time it is straight up reading zero pressure.

    The sensor is practically new, I replaced it (along with every other engine sensor) last year when I rebuilt the engine. I have a really hard time believing that I can have 40+ PSI at the filter and zero PSI at the top pf the block (for those that don't know, the oil pressure sensor, and yes it is a sensor and not a switch, is at the back of the block on the top of the valley, rather than in one of the heads). The oil pressure at the sensor is usually about 10-15% less than at the filter. While it could be the sensor itself is going bad, it seems unlikely. I screwed around with it last night, I thought maybe it was due to the fuel and vapor lines rubbing against the wires to the sensor, but after spending several hours last night futzing around with it (most of that was spent trying to fish my 1/4" ratchet out from between the transmission and the fuel/vapor lines after I dropped it like an idiot) and getting them to clear the sensor and its wires, it still showed zero pressure a couple times this morning.


    And now I also am having an issue with the HVAC blower motor. Yesterday it wouldn't come on at all after working just fine before parking at a store. Turned the car off, then back on after a couple minutes, blower started working just fine and kept working all the way home. Started teh truck up this morning to go to work, guess what, blower isn't coming on. Fortunately it's cool in the morning so I just left it off and went on my way. Seems like it's either the blower fuse, the speed switch, the resistor pack, or a bad ground.

    Oh, and I apparently should have replaced the PCV hoses when I rebuilt the engine as well, one of the rubber fittings cracked open at some point which explains the random rough idle I was getting. New ones are on the way, they are surprisingly cheap from Rock Auto, $20 shipped for both of them.

    Soooo much fun.
    2008 H3 Alpha

    "Live free or die: Death is not the worst of evils." - General John Stark

    N1JPA

  2. #2
    Bogger
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    If the oil pressure is reading a fixed number then its a wiring issue. A bad sensor may still be reading something or inconsistently or even wrong values but they will be varianle, a shorted wire will give a random fixed numbet instead. I had a similar issue where my truck was misfiring like crazy, the fuel pressure was in the single digits and was always a fixed number. Adter back and forth it was a shorted it out wire.
    Whatever it is, good luck!
    06 H3, Birch White, Lux , Cooper AT3 35s, Borla Performance Cat-back, Bilsteins front w/ 1/2" extended stops, Hunner sleeve, Air Doc w/ K&N filter, Oem Roof lights, 55W HID Headlights and 35W Fog lights.

    09 H3 V8, LS376/480 Conversion, 3000 stall, Arctic Silver, 35s, XD Rockstar Wheels 17x8 Front 17x9 Rear, OEM Sliders, 40K External Trans Cooler, Bilstein 5160s front 5100 rear, O.D. Steering Bracket, Daystar 1" Body Lift, Borla Performance Cat-Back, custom intake pipe & K&N filter, Custom PCM tune, Pioneer DVD unit, Aurora 40" LED Light Bar, 50 W HID Headlights

  3. #3
    El Diablo
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    Random, seemingly unrelated electrical issues typically point to grounds, weak battery terminals or connections, a weak battery, the fuse box connector underneath the fuse panel in the engine compartment, or a frayed wire like amrg pointed out.

  4. #4
    Bogger
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    I watched it more closely last night. I am definitely keeping pressure based on the MaxTow gauge. At one point I had about 50psi on the MaxTow while the computer thought it was seeing 0.00 psi. Oddly enough it mainly happens during acceleration like I mentioned, but I cannot reproduce it when revving the engine while standing still. Seems it is definitely due to shifting weight/momentum. It very well could be a short or bad ground, except all grounds for sensors go straight back to the ECU. So it's either a short in the harness (which is seeming more likely due to the issues I have been having) or there is something wrong inside the ECU (which seems improbable given the symptoms).

    As for the blower, I checked everything this morning and it's all pointing to a failed blower. Figures I can get it online for half the price of anything locally, even for the same ACDelco part. Thankfully it's going to be cooler the next few days, the last couple days were close to 100 degrees, and a black truck baking in the sun all day makes an uncomfortable ride home while wearing dress clothes.
    2008 H3 Alpha

    "Live free or die: Death is not the worst of evils." - General John Stark

    N1JPA

  5. #5
    Bogger
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    Did you have the blower harness recall done? If not, now wld be a good time (rule it out completely as the culprit)
    06 H3, Birch White, Lux , Cooper AT3 35s, Borla Performance Cat-back, Bilsteins front w/ 1/2" extended stops, Hunner sleeve, Air Doc w/ K&N filter, Oem Roof lights, 55W HID Headlights and 35W Fog lights.

    09 H3 V8, LS376/480 Conversion, 3000 stall, Arctic Silver, 35s, XD Rockstar Wheels 17x8 Front 17x9 Rear, OEM Sliders, 40K External Trans Cooler, Bilstein 5160s front 5100 rear, O.D. Steering Bracket, Daystar 1" Body Lift, Borla Performance Cat-Back, custom intake pipe & K&N filter, Custom PCM tune, Pioneer DVD unit, Aurora 40" LED Light Bar, 50 W HID Headlights

  6. #6
    Street Tire
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    Hmmm ...can you plz explain more about the blower harness recall?


    AMRG: When the oil pressure wire shorted out, can I ask where it shorted? Was it rubbing up against something?

    Thanks!!
    Jeepwalker

    '07 H3 Advent/Lux
    Jeep XJ, ZJ, WJ
    Ram & GMC 4x4's
    Toyota Hilux

  7. #7
    El Diablo
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  8. #8
    Street Tire
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    Thanks, I'll have to look into that.
    Jeepwalker

    '07 H3 Advent/Lux
    Jeep XJ, ZJ, WJ
    Ram & GMC 4x4's
    Toyota Hilux

  9. #9
    Bogger
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    Amrg wins the prize. Decided to take a look at the engine wiring harness before leaving work, you know, wiggle it around and see if anything comes to mind. Lo and behold I put my hand on the section at the back of the intake and feel the plastic corrugated tubing disintegrating. Decide to climb up and take a look since I also felt a sharp edge back there.

    Guess what wire is tan with a white stripe? Yep, the signal wire for the oil pressure sensor.

    Sent from my SM-N950U using Tapatalk
    2008 H3 Alpha

    "Live free or die: Death is not the worst of evils." - General John Stark

    N1JPA

  10. #10
    Bogger
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    So another project I am probably going to do when I can get some downtime for the Alpha is re-wrap the entire engine harness. I'm betting my crank sensor is a similar but far more intermittent issue.

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    2008 H3 Alpha

    "Live free or die: Death is not the worst of evils." - General John Stark

    N1JPA

  11. #11
    Bogger
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    Quote Originally Posted by amrg View Post
    Did you have the blower harness recall done? If not, now wld be a good time (rule it out completely as the culprit)
    Pretty sure I checked recalls on this Alpha and there were not any outstanding ones. I went through the testing outlined in the service manual and everything checked out, so it's most likely the blower motor decided to suffer an open winding or something. 178,000 miles seems not too unreasonable for it to last. Thankfully it looks relatively easy to replace without needing to pull the entire dash like some cars.

    Sent from my SM-N950U using Tapatalk
    2008 H3 Alpha

    "Live free or die: Death is not the worst of evils." - General John Stark

    N1JPA

  12. #12
    Bogger
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    @jeepwalker
    I may not have been clear, My fuel pressure sensor was shorted out not the oil pressure sensor, it was touching the downpipes of the exhaust and burned out. The sensor is located between the engine and the firewall and is visible from under the truck with the plates out.
    Humvee recently had a similar problem, but his was intermittent and got all sort of codes starting from fuel pressure to Fuel pump control module. Ended up being a shorted out wire against the exhaust too at a similar location.

    @Jpaul, hope you got one thing sorted out then! Electricals are a pain.... for me at least!!!
    06 H3, Birch White, Lux , Cooper AT3 35s, Borla Performance Cat-back, Bilsteins front w/ 1/2" extended stops, Hunner sleeve, Air Doc w/ K&N filter, Oem Roof lights, 55W HID Headlights and 35W Fog lights.

    09 H3 V8, LS376/480 Conversion, 3000 stall, Arctic Silver, 35s, XD Rockstar Wheels 17x8 Front 17x9 Rear, OEM Sliders, 40K External Trans Cooler, Bilstein 5160s front 5100 rear, O.D. Steering Bracket, Daystar 1" Body Lift, Borla Performance Cat-Back, custom intake pipe & K&N filter, Custom PCM tune, Pioneer DVD unit, Aurora 40" LED Light Bar, 50 W HID Headlights

  13. The Following User Says Thank You to amrg For This Useful Post:

    JPaul (09-06-2019)

  14. #13
    Bogger
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    Amrg, Electrical is always a pain, even to those of use that do understand it.

    Obviously my problem is that when I rebuilt the engine I upset the delicate balance of the wiring harness so now these things are starting to happen. The corrugated tubing holds up pretty well but over time becomes brittle due to heat, so when I moved everything around it started falling apart. There are a couple other spots I know this is happening, and I am betting that it's happening somewhere along the crank sensor's wiring as well since that is right under the exhaust manifold. Clearly moving forward the next time I do major work like rebuilding/replacing an engine or anything I need to plan on spending time refurbishing the wiring harnesses as well. Probably some additional heat shielding where the split loom is breaking down would be a good idea as well.

    The spot the oil pressure sensor wire was being chafed explains why it was primarily happening only during acceleration, there was apparently just enough movement allowed in the harness that when I would accelerate it would shift backwards just enough to short the wire. The damage to the wire's insulation looks like it might have happened either during installation (though I am pretty sure I would have noticed the tubing missing on that spot and fixed it then) or it just happened to shift downward over a period of time with the metal clamp slowly scraping a peel of the insulation away until it cut deep enough to expose the copper inside.

    I opened up the metal bracket yesterday and had zero issues on my way home. I thought I had some more tubing at home but apparently not so I will be picking some up today at Harbor Freight. Interestingly the split loom tubing there is actually pretty good, far better than the thin garbage you get at Autozone and the like. I bought some from Autozone once and it is thin, doesn't hold its shape well at all, and probably wouldn't last long on general.

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    2008 H3 Alpha

    "Live free or die: Death is not the worst of evils." - General John Stark

    N1JPA

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    Korby7 (09-06-2019)

  16. #14
    Bogger
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    Well, it wasn't the blower motor. Got the new one and plugged it in to make sure I was right, and I wasn't. Spent two hours digging into the wiring and figured out there was a low resistance short to ground somewhere in the wire coming from the fusebox to the blower motor. Started disconnecting the harness starting from the blower motor harness back to the firewall harness. Determined the short was somewhere between the connector at the interior of the firewall and the fusebox. 3 feet of cable is all. Poked around but didn't see anything obvious, pulled the fuseblock out completely, tested again and the short was gone. Tested the fuseblock, no issues. Put it back together a piece at a time and kept checking as I hooked each section together, still no short. Got it all back together and the blower works now.

    What I figure is that something was funky in the fuseblock and pulling it and reseating it took care of the issue. I am pretty sure I have heard of others having the same problem. The reason the blower wasn't working was due to the short diverting too much power to permit the motor to run, but the short wasn't a dead short so it provided enough resistance to keep the fuse from blowing. Hopefully it doesn't happen again, but if it does I will dig into it more. I also noticed that the pin/socket for the blower motor positive supply in the connector between the interior body harness and the firewall harness were overheating and melting the housing. It's working OK for now but later when I have more time I am going to cut the wires at the connector and add a bypass for them. I had to do that on my red H3 for the rear defroster as well. Too much amperage for connectors like that once the terminals start to get old.
    2008 H3 Alpha

    "Live free or die: Death is not the worst of evils." - General John Stark

    N1JPA

  17. #15
    Street Tire
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    I agree, probably a bad connection back there. I've had things like that happen over the years on vehicles. The FIRST thing just about all factory manuals say to start at in the electrical diagnosis tree is to check connectors (or connection points), then possible shorts. Did you notice any bubbling or any bulges under the wire plastic? Hopefully that solves that issue for good.
    Jeepwalker

    '07 H3 Advent/Lux
    Jeep XJ, ZJ, WJ
    Ram & GMC 4x4's
    Toyota Hilux


 

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