gottarollwithit

So i just bought my first Jeep Cherokee. It's a 98' model so it has many of the last gen updates.

However, i bought this car semi broken - the prev owner got stuck in a pit and the car died immediately after he popped out of the rut. The downstream 02 sensor wiring is torn off. It was enough to yank the wires apart at the harness and yank out the 2 prong male connector that plugs into the top of the transmission. Any idea what this connector is for? It has 2 wires, one is black/red and the other is some other kinda black. It has a green weatherseal on the inside of it as well. Neutral safety switch??


More importantly, the engine isn't getting fuel or spark, the voltage and gas gauge is dead, but the engine is able to crank no problem. I don't hear the fuel pump kick on when putting the key in pos 2 and there's no pressure at the rail. I swapped fuel pump relays and it did nothing. Additionally, i put my multimeter on the crank sensor and it reads open between the far left and middle terminals, if the tab is on top, so i guess it is good.

Any ideas?? Maybe a bad ECU, or wiring that's shorting out, which is causing the ECU to not turn on? What else should i be looking for here? Anybody know what else is tied into the harness down where the downstream O2 sensor is?

Thanks!!

freegdr

check fuses in pdc box for current in and out .

Cherockee

First repair all the wiring that's broken, then go through all the fuses, both under the hood and in the passenger kick panel, then check out the ASD relay and be sure its functioning properly. Report back.

ihscoutlover

Gottarollwithit,

Cherockee hit on a couple of things here. First, check all your fuses, and make sure those are in tact and good. Repair any damaged wiring. This is where a FSM(Factory Service Manual)--the bible of your vehicle--comes in handy. It tells you what wires go where, and offers some basic troubleshooting tips as well. I was having numerous problems with mine(still am), but after working out some of the issues, I came to the conclusion that the fuel pump had finally given up the ghost. With no fuel and no spark, the first thing I would consider is the CPS(Crank Position Sensor). However, with some wiring that was damaged, and not really knowing where some of those are located, it might be hard to exactly help you fix it, but we will try. The CPS if its not working, will not send the signal to the ECU to fire the spark plugs. After re-reading your post, if the wiring on the top of the tranny is on the top driver's side, then its the CPS. If its on the top passenger side, the wiring should be for the NSS. The NSS, has either 6 or 8 wires inside its connector. You said a two wire connector, and thus leads me to believe the CPS, and I would strongly urge you to get that from the stealership. Its gonna be a much better part, as I have seen many have issues with parts store ones. Let me see if I can find you a picture of what the wiring on the CPS looks like. Two of these are part #'s, for the part, these went on a '94 with a 4.0 AW4 transmission. The other two are a comparison of the old and new parts together, with the old one being on the top in one picture. The green dot thingy is the spacer that spaces the CPS from the flywheel the proper distance. Let me know if I can be of further assistance.

Jeff

gottarollwithit

Sorry for the noob questions.

Is a PDC the fuse box under the hood on the passenger side???

All of the fuses are OK and i've tried swapping ASD and Fuel Pump relays with JY ones. I have a 98'. Where is the second fuse box and how do i get access it???

As for the downstream O2 sensor, i clipped the wires off so they aren't shorting out anymore.

As for the cranksensor and the various wiring topics... My cranksensor wiring runs from the sensor, back up to the intake, which is where the connector for it is. Dunno where it runs after that. However, the section of the harness that got yanked hard was the downstream O2 sensor. That 02 sensor wiring runs along the top of the transmission and has a 2 prong, male connector that Y splits off of it. The 2 prong connector (black/red and Black/) plugged into the top of the transmission, towards the back of it on the driver's side. That definitely was not a crank sensor b/c that is on the bellhousing. Any idea what this 2 wire sensor is that's atop the transmission?

Can a bad crank sensor kill both fuel pressure and spark??? I thought it was only spark that it controlled.

Due to this, i'm more thinkin that this is an Automatic Shut Down system problem. What do you guys think? Anybody know how this magic system works???

OleBlue

look at the symptoms in the below post, sounds exactly like your issues with no gauges/fuel/spark etc. Suspect the CPS

OleBlue

According to this it can. Thought this may help worth a shot.

Quoted from cj7-tim


A bad CPS does not always show a fault code when the ECU computer is checked with a scan tool. Not all no starts are the CPS, but it is the most common and obvious place to start.

A No Bus display on the instrument panel may be a faulty connection behind the instrument panel and the engine will start and run, or it may be a bad CPS and you have some or all of the symptoms described below. The CPS being defective can sometimes have an effect on the instrument panel.

A bad CPS, will in fact, shut off the spark and sometime, but not always, the fuel pump. Because the ECM is getting no reading from the CPS that the engine is turning over (bad CPS) it will not prime the fuel pump or allow a spark.

A simply test of the CPS that often works is to unplug it and reconnect it. If the motor will start after that, the CPS is highly suspect and should be replaced.


The most likely cause of it cranks and cranks but won't start up is the Crankshaft Position Sensor (CPS) located on the transmission bell housing. Often this part is also referred to as the CranKshaft Position Sensor (CKP) CPS/CKP failure is very common. The CPS/CKP can stop working with no warning or symptoms and the engine will not run or the engine may randomly stall for no apparent reason.

Typical Symptoms –
- Starter cranks and cranks but engine won't start up and run.
- Fuel gauge and voltage gauge may not work or display properly.
- You sometimes will have No Bus on the odometer after 30-60 seconds.
- A failed CPS/CKP may or may not throw a CEL trouble code.
- No spark at the spark plugs.
- Fuel pump should run and prime for 3-5 seconds.

Begin with basic trouble shooting of the start and charge systems. Remove, clean, and firmly reconnect all the wires and cables to the battery, starter, and alternator. Look for corroded or damaged cables or connectors and replace as needed. Do the same for the grounding wires from the starter to engine block, and from the battery and engine to the Jeep's frame/body. You must remove, scrape, and clean until shiny, the cable/wire ends, and whatever they bolt to. Jeeps do not tolerate low voltage, bad connections, or poor grounds and the ECM/ECU may behave oddly until you remedy this.

Exchange the fuel pump relay and the ASD relay with one of the other similar ones in the PDC to eliminate the relays as the cause of the no-start. Check the ASD relay fuse.

Confirm that the fuel pump to runs for 3-5 seconds when you turn the ignition key to ON.

Eliminate the NSS as a cause of no start. Wiggle the shift lever at the same time you try to start. Put the transmission in Neutral and do the same. Do the reverse lights come on when the shifter is in Reverse?

Inspect the wires and wire connectors at the O2 sensors on the exhausts pipe. A short circuit from melted insulation or from broken O2 sensor wires can blow a fuse and the ECU/ECM will loose communication. Don’t get tunnel vision and assume the sensor is bad (unless it tests bad with a meter). Damaged wiring or a dirty connector can inhibit the signal from making it to the computer. Inspect/test/clean/repair wiring or connectors as necessary.

If the CPS/CKP is failed sometimes the OBD-II trouble code reader cannot make a connection to the ECU/computer or cannot read Check Engine Light/MIL codes because the CPS/CKP has failed. Disconnect the code reader, disconnect the CPS/CKP wire connector, and reconnect the code reader. If the code reader establishes contact with the ECU and scans, your CPS/CKP is failed and needs to be replaced.

Crank Position Sensors can have intermittent “thermal failure”. This means that the CPS/CKP fails when the engine gets hot, but works again (and will test as “good”) when it cools back down.

Diagnostic steps to confirm the CPS is the cause of your no-start
1) You should be able to verify a bad cps, by unplugging it, and turning the ignition key to on. If the voltage gauge and/or the fuel gauge now display correctly and/or the No-Bus is gone, replace the CPS.
2) If the CEL does not come on when the key is turned to the RUN position... then the CPS/CKP is bad.
3) Unplugging and reconnecting the CPS sensor where it connect to the main harness near the back of the intake manifold usually resets the ECU and if the jeep fires right up after doing this you can bet that the CPS is faulty and needs to be replaced.

The 2000 and 2001 will have the CPS in the same location on the bell housing, but the wire connector is near the Transfer Case, not as shown in the diagram below. Simply follow the wire from the sensor to the connector.

CPS Testing

Crankshaft Position Sensor Connector (CPS/CKP)


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TESTING PROCEDURE 1991 – 2001 4.0L H.O. engines

1. Near the rear of intake manifold, disconnect sensor pigtail harness connector from main wiring harness.
2. Place an ohmmeter across terminals B and C (See Image). Ohmmeter should be set to 1K-to-1OK scale for this test.
3. The meter reading should be open (infinite resistance). Replace sensor if a low resistance is indicated.

TESTING PROCEDURE for 1987 – 1990 4.0 L engines

Test # 1 - Get a volt/ohm meter and set it to read 0 - 500 ohms. Unplug the CPS and measure across the CPS connector's A & B leads. Your meter should show a CPS resistance of between 125 – 275 Ohms. . If the CPS is out of that range by much, replace it.

Test # 2 - You'll need a helper for this one. Set the volt/ohm meter to read 0 - 5 AC volts or the closest AC Volts scale your meter has to this range. Measure across the CPS leads for voltage generated as your helper cranks the engine. (The engine can't fire up without the CPS connected but watch for moving parts just the same!) The meter should show .5 - .8 VAC when cranking. (That's between 1/2 and 1 volt AC.) If it's below .5vac, replace it.
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Radi

Two-wire plug on the trans is probably the speed sensor.

freegdr

All fuses ok ....like power on both sides or they look ok ?

CCKen

That's the transfer case light (instrument cluster) switch connector for a NP231J transfer case.

Edit: You'll have to see if the recepticle on the TC switch is damaged (switch replacement) and/or the harness connector is damaged.

CCKen

Concerning no fuel quantity and voltmeter reading on your instrument cluster; they are the only readings you'll get with the ignition switch in the run position and the engine is not running. If you don't get these two readouts there's a possibility that the CCD Data Bus is dead. This is where your instrument readings come from.

Why would the CCD Data Bus be dead? Many reasons, one of which is that the '98 XJ AW4 transmission has two transmission speed sensors, one is Input speed and the other is Output speed. Both sensors are mounted on the left side of the transmission, They are Blue in color. If any of the speed sensors wiring is shorted (or possibly open) it will affect the Transmission Control Module (TCM), which in turn will corrupt the CCD Data Bus. I think the transmission speed sensor wiring is in the same loom that the TC mode switch and downstream O2S wiring is in. The transmission/TC wiring looms come out in the engine bay near the transmission dipstick tube. There are three connectors there: the Transmission Range Sensor (NSS) connector, Transmission Control Assembly, and connector C107. If the impact of the Jeep going in a ditch was enough to rip out the downstrream O2S and the TC Mode switch connectors you will need to inspect the entire length of these looms and see where it/they were snagged and determine what/how many wires have been damaged. Examine the Transmission Speed Sensor connectors closely.

The fuse Juntion Block (JB) you're looking for is in the passenger footwell. There's a small cover over it that pops off. Below is a pic of the JB. The fuse you should be interested in is #11 (20 Amp). #11 powers the fuel pump relay and ASD relay control coils. If this fuse is blown these relays will not pull in and thus not power the Fuel Pump, Ignition Coil, O2S heaters, and Fuel Injectors.

The ASD relay control coil gets a ground from the PCM when it detects the CPS has detected crankshaft rotation, then the relay coil pulls in the power contact of the relay to power the fuel and ignition essentials (povided F11 is okay). The fuel pump relay control coil gets its ground from the PCM like the ASD relay, except the fuel pump relay will get a momentary ground from the PCM when the ignition switch is put in the RUN position. This will operate the fuel pump for 1-2 seconds to pressurize the fuel rail. When the engine is running, the PCM will provide a continuous ground to the control coil.

CCKen

To see if your CCD Data Bus is dead, and the PCM is operating properly, regarding no volts or fuel quantity readout, perform the following test:

Instrument Cluster Actuator Test

(1) Begin the test with the ignition switch in the Off position.

(2) Depress the trip odometer reset button.

(3) While holding the trip odometer reset button depressed, turn the ignition switch to the On position, but do not start the engine.

(4) Release the trip odometer reset button.

(5) The gauge(s) should cycle through their ranges, stopping at intermediate readings at two second intervals. The indicator lamp(s) should cycle on and off.

(6) The instrument cluster will automatically exit the self-diagnostic mode and return to normal operation at the completion of the test, if the ignition switch is turned to the Off position during the test, or if a vehicle speed message indicating that the vehicle is moving is received from the PCM on the CCD data bus during the test.

If the instruments don't react to this test the PCM is not working properly or the CCD Data Bus is dead.

gottarollwithit

So, all fuses by visual inspection are OK. This includes those inside the passenger footwell and those under the hood.

Next step is to unplug the Crank Pos Sensor and see if it makes my gauges work again. If not, it's time to pull the rear wire harness and inspect it.

CCKen's theory sounds really, really plausible to me.

While the Crank sensor is still a possibility, it just sounds TOO coincidental that it crapped out at the same time as this guy snagging an 02 sensor on his way out of a pit.

gottarollwithit

OK, update time now that i've done some testing.

-Still no fuel pressure at the rail or spark.
-There's no power at the coil.

-There's about 1.25v at the fuel pump, regardless of whether i jump the FP relay or use the relay itself.
-Obviously, the FP never spins up, even when i jump it from the relay.

-I get a solid 12v at the fuse box under the hood (based on the + wire under the second cover and grounding onto the block)
-At the fuse box under the hood, there is a solid 12v at each of the large fuse terminals.
-I measure 12v at the ASD and fuel pump relay terminals.

-I jumped the ASD relay from 30 to 87 and it did nothing

-I disconnected the crank sensor and my fuel and voltage gauges still don't work.
-I resistance tested the B and C terminals on the crank sensor and it reads open. Still a possibility?

-I tested the PCM computer by doing the diagnostic test of holding the odo reset button down and turn the key, and it seems to work just fine.

-Also, the Neutral safety switch seems to be having some issues now. When in Park, sometimes it'll crank, othertimes it doesn't. If i jiggle the selector, it usually will. In Neutral, it always cranks. It will not crank when in gear though. From what i understand, the NSS only controls the ability to crank, not spark or fuel.

Based on all of this, got any new thoughts??? Maybe the fuel pump wiring is on the same harness as the O2 sensor and the wiring got mangled under the corrugated sheathing, which lead to only having 1.25v??

Anybody know how to manually spin up the fuel pump using another car battery? There's a 4 pin connector and i dunno which pins to use...

I'm starting to think that i'm in a bit over my head. Anybody in the Bay Area interested in taking a look??

CCKen

At least you know the PCM and the CCD Bus to your instrument cluster is still alive by doing the actuator test.

Did you inspect ALL the wiring under the vehicle to see where damage was done? Including the three connectors near the transmission dipstick tube? All the wiring and connectors in the engine bay for that matter.

Based on what you said about the transmission range sensor (NSS) there's a possibility that the wiring for it is diked up as well.

Don't know why you would be jumpering the ASD relay. Unless you did this while the engine was cranking. The Fuel Pump circuit is seperate from the ASD circuit. If you jumped ASD relay pin socket 30 and 87 that would put power to the fuel injectors, ignition coil, and O2S heaters but not the fuel pump. Until you determine if there is other damage to the wiring you could jumper relays all day and still get nowhere.

If all the fuses are okay, it would appear that there are no shorts to ground in the systems, only opens. There has to be more damage to wiring somewhere.

I'll get you a pinout image of the FP connector so you can properly check power to the pump (not the fuel quantity sender circuit), and jump the pump if you want.