I hadn't driven my 2001 Jaguar S-Type 4.0 in a couple weeks and the battery was dead. I jump started it and drove it for about 20 highway miles to make sure the battery was charged. It drove fine. When I got back, I turned the car off and back on to make sure it would start. It did, but it idled rough and wasn't very responsive when I tried to rev the engine. I turned it off and tried starting it again. It just cranks and won't start.

I noticed the check engine light was on, so I pulled the following 2 codes: P0456 (EVAP Emission Control System Leak Very Small) and P1587 (Throttle Control Unit Modulated Command Malfunction).

Should I start replacing parts or do more diagnosis.

Thanks!

 

I would remove the ground cable from the battery, charge it (slow charge) and then reconnect.
This does a HARD RESET and ensures that the battery is fully charged.

Could be a failed throttle assy?

 

Likely the battery. May or may not recover.

 

Do you have a part number for the throttle assembly? Are the throttle assemblies the same for the 4.0 vs 3.0 engines? Refurbished assemblies appear much more expensive than used. Is it worth trying to replace it with a used one?

 

The 3.0 and 4.0 throttles are similar (electrically) but the coolant lines have different routings.

I installed a 3.0 throttle on a 4.0 engine by bending the coolant lines on the throttle housing.
(emergency repair but engine ran normally)
The 4.0 throttle has the coolant lines on the manifold and the 3.0 V6 has the lines on the throttle body.

The customer chose to leave the 3.0 throttle on the 4.0 engine so I did not argue.

 

Twenty minutes on the road isn't nearly enough to replenish a discharged battery. Even if the starter cranking speed seems okay, do yourself a YUGE favor and charge that poor battery. This is just a basic prerequisite for any electrical troubleshooting, so please don't skip this important step. You can't rely on the alternator to have recharged the battery. A trickle charger won't cut it, either, so don't waste your time. If you don't have access to a charger, take the battery to any auto parts store. They can test it for you, and most places will recharge it for free if needed.


Ignore P0456 for now. That is a very common fault, and won't affect starting (or lack thereof) one bit.

P1587? That's far more uncommon. However, look at this reference chart. I'm not sure it's related to the no start condition, and may be just a spurious code generated due to low voltage:

http://www.jagrepair.com/images/Auto...os/PE20001.PDF


Look at the "Default Action" column to see what happens when this code is set. If only one channel has failed, nothing happens. If both channels have failed, you'd get restricted performance, etc., but I don't see anything saying the engine won't start. That's what makes me think it's a red herring, and may clear after the battery is fully charged.

If recharging the battery is still no help, you may have fallen into a bit of no-man's land as far as the computer is concerned. OBD fault codes are only reported for emissions-related problems. But if you've got a no-start condition, the computer still knows why but isn't going to tell you because it's not an emissions problem. The computer just stands there with its arms crossed and says it's not programmed to tell you that, so isn't going to do it. I believe a dealer-level computer interface can report why (no spark, for example), but we mortals will have to resort to basic troubleshooting such as checking for spark, fuel pressure, etc. It's a bit of a Catch-22.

Another possibility is the anti-theft system may have been triggered during all this commotion. So before digging deeper anywhere else, check the operation of the security system. Watch the red LED at the base of the windshield. Here's how the light is supposed to behave if all is good and no faults are present:

First, lock the car with the key fob. Press the lock button a second time to set the alarm system. The horn should chirp once. Watch the little red light. It should flash once every few seconds to show the system is armed. Now press the key fob unlock button twice to unlock all the doors. The red light should go out. Now hop in the driver's seat and turn the key to RUN (Not start yet). The red light should come on solid ONCE for about 3 seconds and then go out. If it flashes anything after that, you've got a stored fault and the security system may have inhibited the fuel pump.

 

Took the battery back where I bought it and it checked out bad, so they gave me a new one (under warranty). I also noticed that fuse #17 (Fuel pump) in the trunk was blown, so I replaced it. Car still just cranks and won't start. Fuel issue? kr98664 mentioned "the anti-theft system may have been triggered during all this commotion" and "the security system may have inhibited the fuel pump". I also noticed after putting the new battery in, the key fob doesn't work anymore. Coincidence? I was going to try a new fob battery. Can I test the PATS light without the fob?

Also, can I swap R6 and R7 on the trunk fuse box to see if it may be the Fuel Pump relay switch?

 

Can I test the PATS light without the fob?

The PATS will activate upon the IGNITION SWITCH ON.
If the light flashes for sixty seconds and then displays a 'flash-code', you have your answer.

Have you checked for DTCs?????????????
Any OBDII 'code-reader' will work.

 

The PATS light blinks about every second when the car is locked. When I turn the ignition on, it's solid red for about 4 seconds and then turns off. My OBDII scanner doesn't show any codes. I did notice something odd - every time I lock of unlock the driver door with the key, I hear a sound like a duck quacking. Upon further inspection, the picture shows what is making the sound (AAMP of America) and it also vibrates at the same time. Sound defective? What is it?

 

Per the Google, AAMP of 'Merica is an aftermarket supplier of electronic goodies, such as security systems, backup cameras, entertainment, etc.:

https://aampglobal.com/home/passenger/

No idea what that particular relay does. Does your car have any aftermarket equipment? Whatever that relay does, it's a simple on/off device. The quacking sound is probably that relay rapidly cycling back and forth, instead of staying put in the commanded position (on or off). Two possible causes for this:

1) Defective relay

2) Low voltage to the internal electromagnet coil

Is this problem causing the no start? Could be, since we don't really know its purpose. It should be easy enough to test. Unwrap the tape to expose the wire connections. Leave the wires connected and backprobe if possible. If you can't do that, back the terminals off slightly so you can snake a meter lead in there. Terminals 85 and 86 are for the electromagnet coil. Make sure you've got steady battery voltage across the two terminals when you unlock the door. Remember, test voltage with all wiring connected for the most accurate results.

If the voltage checks good yet the relay still vibrates, replace it. Despite the company name on the relay, it looks like a standard Bosch relay. Take it to any parts store and they should be able to match up a replacement.

If the voltage is low or unsteady, you'll have to dig a bit deeper to find the source.

 

Double check the fuse has not blown again.

If still good, check to see if you are getting fuel pressure at the injector rail. Connect a mechanical gauge to the test port on the fuel rail. I've added an arrow to this picture from the training guide, showing the location on the early V8:




If you don't have a test gauge, you can borrow one for free from some auto parts stores such as Autozone and others.

 

I'm beginning to think I have a couple problems and they may not be related. I replaced the relay with a new one and get the same noise - about one second of rapid clicking when I lock/unlock the car with the key, so I don't think the original relay was bad - I may try to test it. I'd like to test the wires going to this relay, so can you tell me how much voltage there should be running to this relay? I still don't know what the relay is for, but can see that the wires run through the firewall and connect to other wires under the dash on the driver side.

I think I may have an electrical problem. Aside from this replay, here is a bit of history: About 2 years ago I replaced the battery because it tested bad. About six months ago, the battery tested bad and was still under warranty, so I replaced it. Last week, the battery tested bad and was still under warranty, so I replaced it again. Fuse 17 in the trunk (fuel pump) was also bad, so I replaced it. We only drive the car maybe once a week, but it seems like something may be discharging the battery over time and also frying it.

 

I wish we knew the purpose of this extra relay. Since it seems to be energized when you unlock the door, I'm guessing it's part of a security system. Kinda odd, as the factory system is quite good, but maybe it was a belt and suspenders approach. Could be a dealer made good money selling this add-on, and didn't let the presence of a good OEM system stop them.

Regardless of its function, it's easy enough to test this relay. Terminals 85 and 86 energize the internal electromagnet. It's not polarity sensitive. Supply battery power to one terminal and ground to the other. You should hear and feel a satisfying click as the electromagnet powers up and pulls the internal switch contacts into position. The relay should not buzz or quack, but only make a single solid click. Remove power from the electromagnet, and there should be a second click as the switch contacts relax to the spring-loaded position. This second click is often not as strong as the first.

When the electromagnet is energized, terminal 30 is connected to 87A. When de-energized, 30 is connected to 87. Not sure how this may have been integrated into the vehicle wiring, but it's easy enough to simulate.

Unplug the relay and try starting without it. This would simulate the proper scenario for engine start if this relay was intended to ground out something when the alarm was tripped.

If no joy, leave the relay out and connect a jumper between 30 and 87A. This would simulate the relay being energized.

If still no joy, connect the jumper between 30 and 87.

Not sure what to suggest after that.

 

Three batteries in two years? Where are you getting them? Might be time to consider a different brand.

Even if something is excessively draining the battery while parked, you can get around this while troubleshooting. Put the battery on a charger, and make sure it's fully charged before trying anything. Even if you do have an external drain, this little workaround will still let the engine start. You can then come back later and work the battery drain problem some other time at your convenience.

Have you rechecked the fuel pump fuse?

Have you verified fuel pressure at the injector rail?

 

I did try to unplug the relay and the car still won't start.

The fob is an aftermarket fob and one of the features is that it will roll down all windows an inch or two after the doors are locked. Mainly used in hot weather. Could this be the use of the relay or was this feature standard when the car was new?

Yes, the fuel pump fuse still looks good.

You're right. I think I'll try to get the car started first, then work on the electrical. It's possible that it's just a bad fuel pump. Probably time to take it to an ACTUAL mechanic.

 

The factory fob has a "global open" feature. IIRC, this has to be enabled via dealer-level software. We mere mortals don't have access to select this feature on or off. When enabled, click the unlock button twice and hold it. All windows (and sunroof) will drive open for as long as you hold the button. I have always wished it had a feature to open all windows (but not the sunroof) about half an inch and stop, for parking on a hot day. Is that how your fob works? Or do the windows keep opening if you hold the button?

It's possible we've solved the mystery of this extra relay, if it's for the windows. Does this magic fob have a remote start or other mythical features? It still does not seem right that the relay would buzz, however. And we still don't know if it could be connected to the no-start condition.

For the no-start, I'd suggest checking fuel pressure at the injector rail. That will guide the next steps in troubleshooting.

 

Got fuel pressure test kit from local auto store and as I suspected, there is zero pressure. I pulled the back seat and don't hear the pump priming, so I'm guessing it's either the pump or something electrical that is not operating the pump.

Also, the fob is a Autopage XT-33. I found an online manual and it appears that there should be a remote start feature by pressing "*". When I do this, the car locks and then does nothing. There also appears to be a valet button (small, red) under the dash.

 

Sounds like you are hot on the trail. Let us know what you find.

 

Wanted to give a final update. I took the Jaguar to a mechanic and they determined that the fuel pump was locked up. After a new pump was put in, it works fine. They didn't know much about the relay other than they also thought it was part of the security and recommended I take it to someone who specializes in that.

Thanks to everyone!