Hi everyone, long time since I've been on the Forum, I'm hoping I can get some help with a fault.

Torque Pro gave me a 'P0117 - Powertrain - Engine Coolant Temperature Circuit Low Input'.

The results of this fault seem to be causing some weird things to happen that I don't understand. After a long run on a motorway, I go into Town where there's the inevitable traffic lights, turns etc that obviously slow me down. The moment she goes onto idle, I get an Engine Malfunction - Restricted Performance warning, the Temperature Gauge drops and flickers around zero, the engine gradually cuts out, this doesn't happen unless the engine is well hot and been running a long time. If I manage to keep the engine running, it splutters until I get some decent revs going, then it's fine until it idles again. The only way out of this is to rev the engine to around 2k then the Restricted Performance light goes off, and the Temp Gauge comes back up to normal. Torque Pro is registering the Coolant about 98° which seems to be normal?

Obviously something wrong with the Cooling system, but I wondered if the behaviour of the car prompts anyone with where to start looking?

My absence on the Forum is complicated due to health, but it means I am unable to spend a long time searching for a fault in the wrong area(s) - hence my post.

Thanks in anticipation as always for any help..
Paul

 

This should help with some direction, but as you see, its a somewhat step by step evaluation to a solution.
My initial attempt would be to replace the sensor, this way you know your dealing with a good unit. Thus also checking the connection to the harness. From there its a tracing process, checking for bared, corroded wire(s) or loose connection(s).

Engine Coolant Temperature Circuit Low

What does this mean?

OBD2 Code P0117 Jaguar definition:
The ECT (Engine coolant temperature) sensor is a thermistor located in the engine block or other coolant passage. It changes resistance with changes in temperature of the coolant that it’s in contact with. It’s usually a two wire sensor. One wire is a 5 volt reference from PCM (Powertrain Control Module) and the other is a ground supplied from PCM. As the temperature of the coolant changes, the resistance of the sensor changes. When the engine is cold, the resistance is high. When the engine is warm, the resistance is low. If the PCM detects a signal voltage lower than the normal operating range of the sensor then P0117 Jaguar code will set.

Symptoms

Possible sumptoms of OBD code P0117 Jaguar
Potential symptoms include: MIL (Malfunction Indicator Lamp) illumination Poor fuel economy Poor drivability Engine may run rough or blow black smoke out the tailpipe May not idle May start and then die

Causes

Possible causes of OBD code P0117 Jaguar
Potential causes of the P0117 Jaguar code include: Bad ECT sensor Short to ground on ECT signal circuit Faulty or damaged connectors Wiring harness damaged Loose terminals at ECT or PCM POSSI JaguarBLY an overheated engine Bad PCM

Possible Solutions

Since this code is for an abnormally low signal to the PCM from the ECT, the PCM saw a excessively “hot” condition in the engine coolant. This could be due to faulty ECT sensor or wiring, but it could, conceivably, be caused by an overheated engine.So if your engine was overheated diagnose that first. Having said that here are the possible solutions: Using a scan tool, with KOEO (Key on engine off) check the ECT reading on the display. On a cold engine the ECT reading should match the IAT (Intake Air Temperature) sensor reading. If it doesn’t, replace the ECT sensor.1. If the ECT reading is showing an excessively hot reading, for example more than 260 deg. F, then unplug the ECT sensor. This should cause the ECT reading to drop to the extreme cold reading (around -30 deg.F or so). If it does, replace the sensor, because it’s internally shorted. If it doesn’t change the reading, the check for a short to ground on the signal circuit of the ECT wiring. It could be that the two ECT wires are shorted to each other. Look for any chafing or melted wiring. Repair as necessary. a. If you can’t find any wiring problems and the ECT reading doesn’t drop to the extreme coldest when unplugged, then, check for voltage coming out of the PCM on the signal wire’s pin at the PCM connector. If there isn’t any voltage, or it is low, then the PCM may be bad. NOTE: On some models it is possible for the 5 Volt reference signal to be temperarily shorted. This can happen if an engine sensor internally shorts the 5 Volt reference. Since the 5 Volt reference is a “shared” circuit on many models, this will cause it to be abnormally low. Usually, though this will be accompanied by several other sensor codes. If you suspect that may be the case, unplug each sensor until the 5 Volt reference reappears. The last sensor unplugged is the offending sensor. Replace and recheck the signal wire from the PCM connector 2. If the scan tool ECT reading seems normal at this time then the problem may be intermittent. Use a “wiggle” test to manipulate the wiring harness and connectors while watching the ECT reading on the scan tool. Repair any wiring or connectors that are loose or corroded. You could check the Freeze frame data if your scan tool has that function. It will show the ECT reading when the failure occurred. If it shows the reading to be at the hottest extreme then replace the ECT sensor and see if the code reappears.

 

I am not an expert by any sense of the imagination -- like Highorse, Motorcarman, Addicted2Boost etc --- but this rings a very loud bell after reading the previous post. I had an XJ6 that while on a trip started running horribly, mileage dropped, etc. Testing showed the coolant temp sensor was forcing the car to run full rich, thinking the car was trying to warm up. The sensor was replaced, but the symptoms remained. Ultimately, a fellow who was once president of the national Jag organization and worked at a shop in the Atlanta area -- after extensive investigation -- found that the place where the wiring clicked into the sensor was corroded inside, causing the spurious signal. He cut a replacement fitting off a donor vehicle in the yard, spliced it in and all was right with the world.

I have no idea if this little tale will help, but it's worth checking out that the wiring to the sensor itself is performing properly.

 

Thanks for the detailed reply Highhorse, everything you have suggested does 'fit' with the problem I am experiencing. You have reminded me of some fairly recent issues that now need to be considered...

The Temp Sensor is an after market one, and has been in there around 3 years when I changed the engine for the Jag replacement one. More recently, about 6/7 months ago, I moved the car off my drive, and {fearing the dreaded Bore Wash you may remember I experienced a long time ago) I left the car on idle, forgetting about it I returned to it with water pouring out of it. I topped up after it cooled and it has started and ran great until this. Your reference to a hot engine reminded me about that. I know of no way I can check if the overheating has caused issue as it runs fine around 2k rpm and above?

Another point worth mentioning. I was on a long run, around 200 miles mostly on a motorway (Highway) and my fuel usage averaged at 27.3 mpg, I have had more than that in the past but only slightly more. Unsure if this is significant?

eliotb: Thanks to you too, I ordered a genuine Jaguar replacement sensor, Thermostat, and Thermostat Sealing ring late last night, here tomorrow so my weekend is sorted lol. My worry now is this pools of water coming out when it was on idle, the only saving grace at the moment is that the car has run so well since then?

I think if I fit the new bits, checking connections, and report back after that?
Paul

 

This diagnosis can go into many different directions. Based on what you’ve told us and given the fact that it’s an AJ26 platform, I’m going to highly recommend that you record everything that you’ve checked so you’ve got the details of what you find.

Obviously start by checking the ECT sensor. If the lock on the connector going to the sensor is broken/missing, (like they all are) replace the connector. Yes, you could use a small amount of rtv/silicone sealer in the meantime but, how many times has this already been done? Unplug the sensor and make sure there’s no wet or green stuff inside of it. If so, I’d replace the sensor and connector. Make sure the sensor and connector are the right ones for each other. M.S. stated that there’s an early and a later ECT sensor and they won’t plug into each other. You can use a later sensor with a later connector as I’ve put on my 98’ XJR. With a small flathead screwdriver, gently push on the backside of the wire terminals to make sure they’re fully seated into the sensor. Also make sure the wires don’t have a sharp bend immediately coming out of the sensor. The copper wires can be broken inside of its insulation even though the insulation isn’t.

If all checks with that, go to the basics first:

Check that the battery is in great shape.

Battery connectors are clean and tight.

Bulkhead connector is clean and tight in the engine compartment. This also includes the mega fuses just to the left of the battery, forward of the spare tire and on all the fuse boxes.

Check your charging system voltage at idle with no loads on. It should read about 14.2-3 volts.

Check the ground strap on the bottom of the engine. If it looks green or is covered in decades of grease, it really needs replaced.

After all this has been done, you really need a live data list of all the engine sensors so we can see what’s going on while the point of failure is occurring.

Without being in front of your car and performing these checks, I speculate that a bad TPS or ECM could be the culprit. You must perform the aforementioned checks first, we’re not here just to throw parts at it.

One last thought... hard reset and check to make sure the little 3” fan under the ECM’s is moving and clean all the dust out so the modules can stay cooler.

 

Jumping in late: replace the crossover pipe and sensor, they usually come as a pair when you buy a new pipe. Since the labor involved is much the same, check Water pump and thermostat and drive belts; refresh the coolant and radiators hoses and enjoy it.

Might just look into the pins at the connector to the MAF sensor for bent ones, clean the MAF sensor too.

 

Hi everyone, I thought I would list where I have got up to, a very late day here, so not ready for a road test yet.

First, I found the connection to the the ECT did indeed have some green contaminate in there, so gave that a good clean, thanks to both Highhorse and Addicted2boost for that input, and while the cooling system was drained I gave it a good flush out.

Also, changed the ECT, and fitted a new Thermostat, the Tower and Pipe are the metal type I fitted some time ago. I agree, it makes sense to change the water pump, especially as I have a new spare, though it is an after market one.

I have been putting off an AC Compressor replacement as it's the proverbial to change, but the one I have on is groaning and the clutch only seems to work intermittently, I have a spare that I know to be good so I will be changing the serpent belt at the same time.

I checked the earths, and being 'belt & braces' I doubled up on the battery earth some time ago, I checked all connections, the AVO meter showed no resistances anywhere I checked, so I am confident that won't be a problem.

Tomorrow the Compressor, Water Pump and belt, then an AC re-gas.. see what happens on a test run.

Thanks for the continued interest and input from everyone, I will come back after a road test - hopefully tomorrow.
Paul

 

Hi again. Finally, I found the issue causing the fault(s), it was barely visible but I think everyone got it right, it was the connector to the Temperature Sensor.

I installed the new Water Pump, proper one with the metal impellers and a metal gasket, new Thermostat and seals, new Temperature Sensor, and a new Serpent Belt. On the first start, 'Restricted Performance', the engine (at cold) showing nothing on the Temperature Gauge, and the engine idling at just over 1k. As the engine warmed, nothing changed, particularly the Temp Gauge and the idle speed. I thought sensor and tried moving it, immediately the idle change to what it should be, around 650 rpm, when I let go, it increased to just over 1k again.

I checked if the inside of the connector was clean, moving the connections with a small screwdriver - it just crumpled, the yellow plastic around it just broke away. Got another from my local yard, and bingo, no problems at all.

A little costly, but I have no worries on the Water Pump, Thermostat, and Temperature Sensor for a while.

Thanks to all who helped and chipped in, solid advice as always.
Paul