4X4 ENGAGING

When you are in 2wd sitting at a stop, in park or neutral, and you press four high, do you hear anything, and does the light continuously flash or revert back to 2wd. How about four lo, you should definitely hear and feel that shift, as well as the gear reduction, does it continue to flash, or revert back to 2wd.

Which wires(what colors) at what switch did you check? At the actuator I am showing a two wire connector, a light blue wire and a black wire. The black wire is shown as hard wired to ground(g105). There is also a front axle switch that has a two wire connector, the same lght blue circuit as the actuator, and a black white hat looks like, in theory, should be grounded by the transfer case control module. There is a bulletin, and a revised schematic, if the new style front axle actuator has been installed.

Ok, I put the truck in the garage where I could get some light on the situation. I un-plugged the connectors at the actuator I am getting around 13vdc when I press the 4wdh or 4wdl buttons. I might be wrong but it sounds like the actuator is not activating. A couple of questions. If it is the actuator and I take it out will the gear oil drain out when it is removed if so where and how much oil do I replace it with. Also what is the other two wires for that go to the transfer above the actuator.

Here are some wiring diagrams (below) and guide on how to test for power, it sounds like a switch has gone out.

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

and

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Please let us know what you find.

Cheers,

When I press the 4wdh or 4wdL I can hear and feel the transfer shift. The light on the 4H or the 4L will flash on the button that is pressed. It does not revert back to 2wd until the 2wd botton is pressed I let it flash for about 10min the night it started doing this. I can hear the switchs or relays in the dash when the 4wd bottons are pressed but I havn't went into the dash and checked them. The wires that I was talking about are the wire that go to the actuator under the front end (not sure what the proper name for it is but it is where the actuator for the 4wd is located or the gear box that locks the front two cv's in to make it 4wd.) one set of wires went directly to the actuator switch and one set go above it on top of this front transfer case(gear box).
Sorry I can't discribe it better. I am a electrical eng. and I don't know certain terms of car parts. It seems to me that everything is working but the final part that makes the 4wd lock-in. So what do you think. If this doesn't help then I will get my brother to discribe it better tomorrow he knows what all of name of these parts are.

Was that 13v using the ground at the connector for the actuator? If you remove the actuator, you should not have much oil leak out, maybe even less to none if you lift the RH front side of the vehicle a bit. If you do have some loss, the fill plug is on the LH side of the differential, above the drain plug toward the front. The fill plug is 15mm, the drain is 13mm. Fill it through the fill hole until fluid runs out.
The wire colors at the actuator should be light blue, and black, is that correct? What are the wire colors that go o the other item that you are speaking of. My guess is, it is a switch that will confirm that the actuator is locked in, this may be what will stop your lights from flashing. The problem with the service information that I am referencing, is it gives no component location description or views. I am going off of the wiring schematic from ALLDATA.

Yes, I plugged the leads of my fluke meter in to the connector for the actuator and this is where I got the 13v from. I am getting power to the actuator but it is not engaging. The wires both look black or dark blue to me I could not tell, But there is not a light blue wire. If the actuator is not working then it is not going to activate the switch at the actuator to sent a signal back to the switch in the dash to let it know that the 4wd has been actatived. I am thinking that the switch above the actuator is working like a limit or some call it a lever switch. Once the actuator is engaged it actavates the switch above the it and it will send a signal back to the dash switch to let it know the the 4wd is actavited.

That switch actually sends the message to the transfer case control module. A quick test would be to jumper the terminals of that switch together. If this stops the lights from flashing, and you are getting the signal to the actuator, then I would suggest a bad actuator. You might be able to bench test the actuator by applying power and ground to it. The symbol in the actuator shows that it is a coil of wire, or a resistor of some sort. You could also check the continuity of the actuator. If it is open, then it is safe to say it's faulty. Service information does not specify an electrical specification for the actuator. It should have some resistance, probably like a fuel injector or similar, possibly 10 to 20 ohms I would guess. Substantially low resistance could indicate shorted windings, excessively high could indicate high resistance or open circuit. I believe the case of the actuator is plastic, so if it was shorted to the case it would not find a path to ground. The following bulletin may interest you if you need to replace the actuator. I am not certain if this upgraded part and procedure address just the complaint as stated, or if it is necessary in the case of any actuator replacement.
Drivetrain - Slow Or No Engagement of Front Axle.

Ok i'm back. I changed the actuator tonight the 4wd works know. But the lights are still flashing on the 4wdh and 4wdl buttons. I also tested the old actuator. It was dead I could not get it to do anything. What do you think is going on with the flashing switchs. I even disconnected the battery to see if this might reset something. Do you think that it could also be the other switch on the hoghead. I will try to jump the switch's wire togeather tomorrow night and see if the lights quits flashing. If you go to O'ReillyAutoParts.com and type in the part # FWD18. This is the switch you are talking about. BWD - Four Wheel Drive Indicator Lamp Switch
Part Number: FWD18

I am wondering if that is not indicating there is a system fault. Explain the flashing in detail, and I will provide you with the info that I have. When you are just turning the truck on, in 2WD, the indicator is?, on solid?. Say you make your first request to 4HI, does all the indicators flash, or just 4HI? Does it continue, or revert back to 2WD? What about 4LO? It is capable of displaying trouble codes through that switch(indicators), it requires jumping a terminal at the DLC connector, are you familiar with that connector?

Fig. 25 Data Link Connector Pin Terminals Displaying Diagnostic Trouble Codes Install jumper wire between DLC terminal 13 and ground, Fig. 25 . The DLC is located under the lefthand side of the instrument panel, right of the steering column. Turn ignition switch to On position. Wait three seconds, then observe transfer case switch status lamps. Reading Diagnostic Trouble Codes The transfer case status lamps will flash to indicate the DTC's stored in memory. If only one DTC is stored in memory, that DTC flashes repeatedly with a three second delay between flash sequences. If more than one DTC is stored in memory, the first DTC flashes once, then the next code is flashed. This sequence continues to flash until the jumper wire is disconnected. Fig. 28 Test A: Status Lamps Flash

You said you disconnected the battery, and one would think that would clear a fault, but here is the code clearing procedure. Clearing Diagnostic Trouble Codes - NV 243 (Electric Shift) Turn ignition switch Off. Remove T-case 20 amp fuse. Wait a minimum of two minutes and 30 seconds, then replace fuse. Cycle ignition switch On and Off 5 times.

When I turn the truck on the 2wd is on and not flashing.
When I switch to 4wdh the 4wdh light flashes and only that light.
When I swtch to 4lo the 4lo light flashes and only that light.
They will keep flashing until I switch back to 2wd.
They are not flashing any codes it is just a constant flash.

Ok, I installed a jumper in the DLC on #13 to ground and swtched the truck on. The 2wd light will flash very dimly and then about a second later all three will flash one time 2wd, 4h, and 4L there is about a five second interval between the flashs. I can bearly see the 2wd flash before all three light flash. I'm not sure if that dim flash even means anything.

I also removed the t-case fuse per the instructions and switched the truck on and off 5 times. Nothing happened.

I pulled the T-Case fuse and switched the truck on and off 5 time again last night. It reset this time. The 4dw is working and the lights stop flashing.

Thanks for all of your help.

Thats good to hear, sorry it took so long for a reply. Glad it was resolved.

I have a 1994 chevy w/t 1500. It has automatic hubs. The hubs will not lock in. The truck has a seperate shifter for the 4x4. When i engage the 4wheel drive nothing happens. Ive checked voltage to the actuater and getting 12volts. I replaced the actuater and still no luck. Is there anything else i can check?
Jerry

Attached is a chart for possible causes of 4WD not engaging.

What is the transfer case model identification?

Some things i forgot to mention... The transfer case was rebuilt about 100,000 miles ago. of that mileage, its only been driven maybe 1000 miles in 4 wheel drive. I have driven in 2h 4L and 4H at various speeds and experience no weird noises or vibrations. Just seems like the front hubs refuse to lock in. Should I get the truck on a lift and make sure my front drive shaft is spining when I engage the 4wheel drive? Also a fuse should be ruled out since Im getting 12volts out of the actuator plug, correct?

also the 4x4 indicator light has never come on since the malfuction. Do you know where the sensors are for the indicator light? Axle? transfer case? both?
I will try and get the model identification for the transfer case soon...

The transfer case switch is located on left frot of transfer case.

Here are the diagnostic procedures.

4WD Will Not Engage

1. Test power to transfer case switch. With ignition on, connect test light to ground and backprobe Brown wire terminal at transfer case switch connector. Test light should light. If so, proceed to next step. If not, inspect 25-amp 4WD fuse in fuse block. If fuse is okay, attach test light to ground and backprobe Pink/White terminal at convenience center. Test light should light. If so, repair open in Brown wire between convenience center and transfer case switch. If not, repair open in Pink/White wire between convenience center and 4WD fuse in fuse block.

2. Test transfer case switch. With transfer case shift selector in 4WD position and ignition on, attach test light to ground and backprobe Light Blue wire terminal at transfer case switch. Test light should light. If so, proceed to next step. If not, replace transfer case switch.

NOTE: Remainder of transfer case electronic testing and diagnosis is performed with transfer case gear selector in 4WD position and ignition on.

3. Test front axle solenoid power circuit. Attach test light to ground and backprobe Light Blue wire terminal of disconnected front axle solenoid. Test light should light. If so, proceed to next step. If not, repair open in Light Blue wire between front axle solenoid and transfer case switch.

4. Test front axle solenoid. Attach test light between Light Blue wire terminal and Black wire terminal of connected front axle solenoid. If test light lights, replace front axle solenoid and proceed to next step. If test light does not light, repair open in Black wire between front axle solenoid and ground. If no opens in circuit are found, replace transfer case relay.


© 2008 Mitchell Repair Information Co., LLC.

Ive had this blazer for about a month now its got about 25000 km on a new motor and the gas mileage has been terrible 9 -10 mpg average its alittle hard to start turns over quite a few times before starting but other then that it runs good and no codes. ive checked the 4wd system think the front actuator didnt release but all is fine there aswell as shaft disengagment. lots of power but im at a loss for words. now alittle while ago i started the truck and shut it off immediatly and the truck didnt start again. had a new iac put into it and that seemed to do the trick. a couple of days ago i did exactly the same thing and it didnt want to start again ( sounded like it wanted to but didnt ) i pulled the fuel pump fuse and reinstalled it and all was well again. im thinking maybe the fuel pump but im not to sure please help alittle 2 expensive at 290km to 53 litres thanks

by the way ithe motor is a 4.3l w-code vortec it had new wires and spark plugs about 2 weeks ago thansk alot
Lee

Lee, common problem with the CPI engines is th efuel pressure regulator blowing out. It is located under the upper plenum on the intake manifold. Not sure if the reg is serviceable seperatly on the 95's, might have to get the whole injector "spider". When the regulator blows, it dumps raw fuel down into the engine.... hard starting and poor mileage are good indicators. Test the fuel pressure as well to be sure it is within spec,If the reg is blown when you check fuel press. then it may be at the higher end of spec because the reg thinks that there is low vacuum like on hard acceleration

I have actually thought of this but with the regulator being bad would that cause irractic rpm spikes or bogging of the motor aswell as a poor idle??? could it also be cold weather i mean i live in ontario right now its about -13 could that be why the mileage is so terrible? does anyone else have a comparsion cold weather situation that relates back to 10 mpg in the winter and better summer . Thanks
Lee

Another question would the tps have anything to do with this porblem of 2 much fuel vs air. off the line it is not a smooth trasaction i mean its not progressive.
theres a dead spot in there then it kicks in. very hard to drive in 4lo. could a bad tps be dumping more fuel making it appear to be regualotr related?

Thanks
Lee

Have you tested the fuel pressure?

i have checked the fuel pressure and it id 62psi

Does it go up when the engine is revved?

fuel pressure spec is 55-61

Hi now in the intake plenum shuld it be wet you can see what looks to be washer as in gold spots. and you can smell what seems to be gas. i have put sea foam through it awhile ago would that cause the washing ( i did it about over 1000kms ago ) should that have dried up? i have just noticed this. well before i checked it after i put the sea foam through it but i assumed that was the sea foam that made it wet inside

Thanks Lee

under the plenum should be dry, fuel leaking from the regulator as discussed before , the cpi units have been updated also from oem for leaking problems

jim

Ok Jim Thanks alot ill replace it and let everyone know what happens Thanks alot

Lee

Transmission problem
1994 Chevy Truck V8 Four Wheel Drive Automatic 170000 miles

Hello to everyone.Just aquired a 94 Z71 ,5.7 ,A/T , 4wd
Unable to get front diff to engage.Been reading a couple of questions on the site with a lot of help I might add,however, this is my problem.
The transfer case will engage,the front diff acutator has 12v, the "ball" device on the top of the transfer case has been removed by me and the ball will depress..one of the three terminals have voltage and here is the kicker..the rear transfer case acutator does not have any voltage...Must tell you that I had no help so I had to engage the transfer case and 4wd with only the ignition switch on but not running,but when the switch was off,so were the hots...
Guys I'm stumped
Could sure use some advise Oh and on top of everything else...we just got 5" of snow last nite...


THanks

Kevin

Today i dissassembled the upper intake. now wuth a closer inspection i can see now that it is actually oil that is in the intake in little puddles. i replaced the pcv valve which in all honesty seemed to be fine to me but changed it anyways and redid all the vacuum connections. cleaned the intake up no more puddles washered down with carb cleaner to almost new now i am gunna see if this puddling returns. has anyone had this happen? and if so did it cause a rough idle at all or the gas mileage problem. cpi doesnt apper to be leaking in the intake no leak key on or turning it over

bye what you say everything is as should be first when you put in 4 wheel the front drive shaft locks you cant turn by hand Yes if all is working in tranfer and there is power to the axle acuater and the ground is good I would replace the front acuater it works buy heating oil. they get slow and then stop working over time you can take it out of front axle and power up to check. Without power and cool the rod or end that is inside dif should be on the short side and when on or warm should be long. Just a tip I have pulled the actuater out pulled the rod all the way out and drill a small hole in the rod and put a small cotter pin to hold it in the engaged pos and reinstall it this will keep the front axle engaged and you still lock in or unlock with transfer only the front axle will always be locked like running with lockout on the older trucks locked in this would work untill you can get a new actuater

Drive Train Axles Bearings problem
1992 Chevy Truck 6 cyl Four Wheel Drive Manual 186000 miles

My four wheel drive is not engaging, no light or anything, I checked for loose wires and found none, I suspect the acuator is bad. My question being, is there some way to test the actuator and make sure it is bad??

You can remove the actuator and then have someone put it in 4 wheel Drive and see if it is working, but before you do that have you check the fuse on the inside fuse box to make sure it is good and it has power going to it on both sides?