4X4 ENGAGING

Tiny
1996Z71
  • 1996 CHEVROLET TRUCK

V8 Four Wheel Drive Automatic 180000 miles. I put it in 4wd last week while I was on a wet slick dirt road at the hunting club. When I got on the paved road I took it out of 4wd. A a few mins. Later I tried to put it back in 4wd and it would not engage. I have 3 buttons on the dash one is 2wd one is 4wdh and one is 4wdl. The light on the 4 high and 4 low would just flash. I can hear the transfer case shifting into 4wd but the front dif is not activating. To make it short the light on the buttons will flash but the front end will not lock in to 4wd. Nothing I that I do will make the 4wd lock-in. I disconnected the plugs from the Actuator Switch one of them had a little water in it but it looked like new inside. I checked the voltage on the plugs with my fluke meter. I was getting around 6 volts on one and around 8volts on the other one. I am guessing the actuator is a normally closed contact because with the I activated the 4wd there was no reading(voltage). I also checked the fuse and it was good.
What is keeping my 4wd from activating?

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Thursday, October 7th, 2010 AT 8:01 PM

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Tiny
FACTORYJACK
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To help me better visulize your condition, I am going to start basic. 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 definately 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 styl 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-pluged 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.

(SOLUTION BELOW)

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Saturday, October 9th, 2010 AT 11:11 PM
Tiny
1996Z71
  • MEMBER

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.

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Sunday, October 10th, 2010 AT 9:32 PM
Tiny
FACTORYJACK
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  • 4,247 POSTS

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.

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Wednesday, October 13th, 2010 AT 1:01 AM
Tiny
1996Z71
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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.

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Thursday, October 14th, 2010 AT 2:52 PM
Tiny
FACTORYJACK
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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.

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Thursday, October 14th, 2010 AT 9:17 PM
Tiny
1996Z71
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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

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Monday, October 25th, 2010 AT 10:15 PM
Tiny
FACTORYJACK
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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?


http://www.2carpros.com/forum/automotive_pictures/309872_42407715_1.gif



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


http://www.2carpros.com/forum/automotive_pictures/309872_42407671_1.jpg



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.

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Wednesday, October 27th, 2010 AT 11:19 PM
Tiny
1996Z71
  • MEMBER

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.

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Tuesday, November 2nd, 2010 AT 10:14 PM
Tiny
1996Z71
  • MEMBER

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.

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Thursday, November 4th, 2010 AT 5:06 PM
Tiny
FACTORYJACK
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Thats good to hear, sorry it took so long for a reply. Glad it was resolved.

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Friday, November 5th, 2010 AT 12:10 AM
Tiny
JMORRISON44
  • 1994 CHEVROLET TRUCK
  • 6 CYL
  • 4WD
  • MANUAL
  • 250,000 MILES
  • MERGED

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

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Tuesday, May 2nd, 2017 AT 4:00 PM
Tiny
KHLOW2008
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Attached is a chart for possible causes of 4WD not engaging.

What is the transfer case model identification?

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Tuesday, May 2nd, 2017 AT 4:00 PM
Tiny
JMORRISON44
  • MEMBER
  • MERGED

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?

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Tuesday, May 2nd, 2017 AT 4:00 PM
Tiny
JMORRISON44
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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.

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Tuesday, May 2nd, 2017 AT 4:00 PM
Tiny
KHLOW2008
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  • 41,996 POSTS
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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.

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Tuesday, May 2nd, 2017 AT 4:00 PM
Tiny
FUNCK_MASTER
  • 1995 CHEVROLET TRUCK
  • MERGED

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

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Tuesday, May 2nd, 2017 AT 4:01 PM
Tiny
FUNCK_MASTER
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  • MERGED

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

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Tuesday, May 2nd, 2017 AT 4:01 PM
Tiny
JACK42
  • MEMBER
  • MERGED

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

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Tuesday, May 2nd, 2017 AT 4:01 PM
Tiny
FUNCK_MASTER
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  • MERGED

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

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Tuesday, May 2nd, 2017 AT 4:01 PM
Tiny
FUNCK_MASTER
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  • MERGED

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

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Tuesday, May 2nd, 2017 AT 4:01 PM

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