I have a 2000 4.0 xj 4x4 with a newly replaced Titan reman engine that is running great. I have replaced the IAC, cleaned the throttle body, replaced the MAP sensor, TPS, crank position sensor, replaced both PCV/CCV elbows and gaskets, water pump, radiator, alternator, battery, and a remanufactured PCM.

When the key is in the run position but not cranked, the relay for the electric cooling fan kicks on (fan starts to barely turn) and is immediately killed by the ASD. If I unplug the ASD, the fan just runs. If I plug the fan relay back in, it becomes a battle between the relays again with the ASD constantly clicking to kill the fan. I have replaced both relays along with everything else listed above. If I pull fuse 11 in the passengers side kick panel, the e-fan - ASD battle stops.

Also, when I am idling in drive, the voltmeter stays at/near 14v, but drops a small amount (13) when A/C or accessories are on - I consider this normal. But when the e-fan kicks on, the volts drop to 11-12 and eventually down to 9 and the 'check gauges' light comes on. When I give it gas or accelerate, voltmeter goes back to normal 14.

To further complicate it, the e-fan is kicking on too soon (in my opinion). Just cranked and idling in drive, the e-fan kicks on when the temps are 170-210. It will cycle on, drop the voltage, run for 10 or so seconds, cycle off, volts go back to normal for 30 or so seconds, e-fan will cycle back on, drop volts, etc. etc. etc.

I feel fairly certain it is a wiring issue, but I can't isolate the problem. I've checked the grounds, which seem good and shiny. I've had the battery and alternator tested numerous times at different parts stores and they are both fine. Belt is new and tight.

I've checked out everything in this forum to no avail...
https://www.cherokeeforum.com/f2/cra...167785/index4/

Any ideas? Thanks for any help!

 

So I removed the e-fan and ASD relays, used a multimeter from pin cavity 85 of e-fan and found 0.01 volts with key off. I then turn the key on and it has 13.8 volts, which I don't think it should. To be clear, I'm referring to post 50 here:
https://www.cherokeeforum.com/f2/cra...167785/index4/

This condition would explain the situation I think? Turn key on and voltage is going to e-fan relay when it shouldn't. But...why?

Thanks in advance.

 

Before doing anything else, I would get an amp clamp for DC and check current draw of that fan when the voltage drops. You might be surprised

 

I'll have to get or borrow one. What would expect to see? What would be the surprise I'd be looking for? I'm a lot better with mechanical than electrical issues so treat me like a dummy.

 

For my year model, a '96, the FSM explains the fan relay is controlled via the PCM providing grounds via either the coolant temp or A/C circuit

It may be different for a 2000, but I doubt it.

imo you need to check if the fan relay is being activated by receiving a ground path, and endeavor to isolate which of the 2 circuits is providing it, and go from there

This could be caused by a full or partial short circuit on a wire or component, such as a sensor, relay or fan

My FSM shows which cavity in the PCM provides earth for A/C and Coolant Temp

 

What I think you will see is one of two possibilities. First you may see the fan amperage increasing as the motor becomes warm. The other is that the available charging capacity of the alternator is reduced as the alternator becomes warm.
First case, replace the fan. Second replace the alternator. If you do, this is a great time to upgrade your alternator to the 160 amp WJ alternator for little or no extra cost

 

Ok thanks. I just learned something new too. Sometimes, it won't crank and you have to either wait or (sometimes) it will fire if you give it gas. I just diagnosed that as being related to the relay issue. As the e-fan and ASD are fighting, the fuel pump is also "pulsing" and not priming the injectors (which were new with the engine). The fuel pump is pulsing on and off in time with the relays when the key is in run, but not started. If I let it pulse on and off for 5 seconds or so, it fires right up after the fuel pump has had a chance to prime the injectors.

I don't think it is the alternator because I've changed it 2x and it has been checked by 2 different stores and it checks out under load testing.

So since it is effecting the fuel pump too, that makes me think it is something in the wiring before the relay. I know there is a relationship (electrically) between the fuel pump and e-fan because fuse #11 in the junction block kills them both. What is before them that could be causing this? I get 12v at fuse 11 with switch on and 11v at both fuel pump and e-fan relays in PDC with switch on but not running.

So, I pulled fuses and relays for both e-fan and fuel pump and ASD is still pulsing and vibrating. So, I checked the voltage and I have 11v going to the ASD with the key in run with neither of the other 2 relays and fuses in place. So, looks like I'm getting voltage straight to the ASD. Is this right?

I followed these instructions again: https://www.cherokeeforum.com/f2/cra...167785/index4/

With fan and ASD relays removed and neg battery cable removed, I had 15M ohms of resistance from ASD cavity slot 85 and PCM connector C3 pin C3. I should have essentially none (<5 ohms). Broken wire?

 

sorry, in a hurry, you could have too much current being pulled by the fan circuit, however,

You asked this:

Turn key on and voltage is going to e-fan relay when it shouldn't. But...why?

I answered because the PCM is providing a ground path for the Fan relay

You need to find out why

(It probably means voltage you measured should be there)

You state electrics are difficult for you

If you ask, I will later link the earlier Diagnostic Manual

I was a technician for a number of years, and on complex equipment that was unfamiliar to me, I almost always follow the diagnostic flowcharts written for that exact purpose

my apologies if I am saying things you already know, its hard to know what level of electrical knowledge people have, I have to start with basic

 

Don't apologize. I struggle with understanding electrics and multimeter use. I can measure voltage, but when it gets into resistance, circuits, etc. I fall apart.

I have the 1970-page service manual if that is what you are referring to, but I'm not aware of a diagnostic flowchart. If it is something different, I would love to have the link to it. I know it will be something simple (lose wire, bad ground, sensor), but I just don't understand how to track it down.

Thank you for your help and patience with me!

 

I think I may be dealing with it on the AC side? When idling, with the AC off, the volts are right at 14 in drive sitting still. When I turn on the blower motor, each increase in fan speed results in a slight decrease in voltage until it is around 12.5. The electric fan kicks on when the temps come up and drops the voltage slightly more.

When I turn the AC on the voltage will drop a bit more to 11-12, but then fall off to 9 and 'check gauges' comes on. It does not do this unless the AC is on. Once the rpms increase, the voltage comes back to 14.

Does this indicate it is on the AC circuit? I feel like a moron for asking all these questions, so thanks for any help.

 

So you may have more than one problem

The voltage dropping with increasing A/C fan speed is indicative of some fault in the blower motor or circuit

This is not the same as the electric radiator cooling fan, although as they should both come on at once, so that is a clue, yes , the problem is almost certainly in the A/C circuit, not the coolant temp circuit

The blower fan, resistor pack and wiring are a known source of problems with too much current

This is not something you can check without appropriate measuring instruments

The A/C clutch is another item that may pull big current

Unfortunately you do need to study the circuit diagrams for your model, and they are not easy to understand, you can post them up

I would be inclined to disconnect the blower motor, I believe it may have a 40A fuse?..see if the problem voltage problem goes away

The PCM becomes disorientated when voltage falls too low, and can cause weird sensor/relay symptoms

 

If you have a reman engine and PCM, means your wiring harness would have undergone considerable flexing, there is an area behind the engine in particular

Noting you seem to have several problems that are all controlled separately by the PCM, ie voltage regulation, E fan, A/C, fuel pump relay,
so I would inspect and clean the PCM main earth wires that are the two next to each other on the side of engine block

I am not sure how many wires run from the PCM to earth, but I think it is more than one

...you can find out in the FSM, under PCM ;cavities

 

for illustration purposes and guidance

@cruiser54 That's three in a row now🤔

 

Probably not related to your issue but in the 200/2001 the ac has no input to the cooling fan, like in the earlier models. It is temp driven only...EXCEPT.. if you trip the "freon" high pressure switch which kills the ac compressor and turns on the cooling fan. It opens the ground for the compressor and supplies a ground to the fan

 

So after weeks and weeks, the solution was about as cheap as it could be. Somehow replacing the fuel pump fuse fixed the problem. Don't ask me how, but it did. I suppose it was somehow feeding back through the circuit. I know many of these posts never finish the story with what the resolution was, so I thought I would close the story with a happy and easy ending. Thanks for all the input!