I recently had a coolant leak on my 04 XJR and my mechanic replaced a few hoses, clamps, and installed a new radiator. I no longer have any leaks but now the RED Engine Coolant Low warning light is always on. This seems to be a very simple circuit but for some reason, I'm having difficulty locating the problem. This is what I know:

1. Coolant level is normal and antifreeze is new.
2. Car does NOT run hot.
3. Sensor is operational, I can measure continuity through the sensor when a magnet is applied and an open circuit when the magnet is removed.
4. The ECL warning light does NOT go off when I short the 2 contacts in the connector going to the instrument cluster (since a GROUND signal needs to be applied.)

The schematic (attached) shows the ECL sensor to be a normally open magnetically controlled switch that either "closes" when the coolant level is low thus applying a GROUND to the instrument cluster which turns on the warning light or "opens" when the coolant level is low, removing the GROUND which turns on the ECL warning light. Either way, since a GROUND is applied to complete the circuit, I would expect a "pull-up" voltage to be present on the wire coming from the instrument cluster as the voltage source but I do not measure any positive potential on the wire even though the ECL light is on. Also, no matter what logic is applied to control the ECL, I'd expect GROUNDING the contact going to the instrument cluster on the connector to either turn the ECL light on or off, yet I get no change. The light remains on so maybe there is an open circuit to the instrument cluster.

What I don't know:
1. Is there a procedure on how to test the ECL warning light circuit?
2. Am I missing something?

Thanks in advance for any helpful suggestions.

 

Try removing the fault code with your code reader.

 

Hi, normally the reed contact on the tank is open, when coolant low a ground connection will be switched. If the warning message is on, there must be ground at input IP5-5 (pin5 of connector IP5) of the instrument cluster. You can proof that by measering continuity against body ground.
If so follow the cable path from CP3-2 to IP5-5, somewhere in between ground could be applied.

If there is no ground on IP5-5 the message could be generated because the controller recognizes open loop between CP3-2 and IP5-5. In this case there is no continuity beetween both pins. The locations of the connectors in between can also be found in the wiring diagram.

Fritz

 

It's most likely the float in the header tank here's a link https://www.jaguarforums.com/forum/x...vations-97440/ to someone else that had the problem and self diagnosed

 

OK. Back to troubleshooting this problem. After all the different things I've tried, I've come to the conclusion that the wire connecting the engine coolant level sensor to the instrument cluster must be open. I have a service manual that only shows a block diagram when what I need is a detailed schematic indicating connector and pin numbers. Is this info available on the forum? Or elsewhere? Thanks to anyone who might have schematics or related info.

 

The full electrical guide for 2004 is here: http://jagrepair.com/images/Electric...al%20Guide.pdf See pages 36, 86, 87.

I think there's been some back-and-forth on the diagnostic path reading the posts above. As flatsix pointed out, presuming the coolant switch is NO, if the wire from the IP got grounded along the way it will show a permanent low coolant warning. If the wire was unplugged from the back of the IP, leaving an open circuit, that would clear the warning. This fault is not code related, no PCM code will be set. The IP also has no monitoring for closed circuit, since it's a NO circuit by design.

The schematic data confirms the switch is NO: IP5-05 LOW ENGINE COOLANT LEVEL WARNING: GROUND WHEN COOLANT LEVEL LOW

 

@mhamilton Thank you so much for the schematics! Problem solved!

Here is what I found... as I said in an earlier post (and thanks to members on this forum) I eliminated the sensor itself when I bench tested it with a DVM and a magnet. I was able to energize the (normally open (NO)) magnetic micro switch by locating a magnet close to the sensor (continuity) and then de-energize it (no continuity) by moving the magnet away, so I assumed it had to be an open wire either between the sensor and the instrument cluster or a missing ground connection to the sensor. While troubleshooting, I did not measure a ground at sensor connector CP3-1, and even when I applied a ground to CP3-2 (wire going to the instrument cluster) the warning light remained on. The schematic shows 2 paths in the circuit as follows. Path 1 connects a ground signal to wiring harness connector CP1-7, to sensor connector CP3-1. Path 2 connects sensor connector CP3-2, to wiring harness connector CP1-6, to wiring harness connector IP8-7, to instrument cluster connector IP5-5. Next, I removed the splash guard under the radiator to expose connector CP1 to look for continuity between connectors CP1-6 to CP3-2, and CP1-7 to CP3-1. I didn't see a release mechanism to disconnect connector CP1 from its mating connector so I just gave it a pull knowing that there was no way it would just pull apart. To my surprise, it disconnected with little to no effort! So, without taking any measurements I reconnected connector CP1 and was met with a distinctive "click" as the 2 connector halves mated. This time, when I tried to pull the connectors apart, they would not budge! WOW! I have no idea how they disconnected in the first place but after reconnecting CP1, the warning light stayed off.