[Battery light flashing, erratic idle]

 

Hi guys!

Driving home from MOT , battery light started flashing. At first from time to time, but 3-4 days along the line it always shows up a few miles after startup. Maybe it has to do with heat because light never flushes immediately after start (cool engine). The usual trigger is when I get on bumpy roads. If light doesn't flash while driving, it almost always flashes when I come to a stop in the parking lot. I normally let the car idle for 30 seconds or so before I shut down the engine and this is when it happens. Lately, idle is also erratic when this happens.

What I checked:

Both belts spin when idling. I've recently changed them actually. I can't see them when I rev, but I doubt they have to do with lights flashing when idling.

Battery voltage: 14.18 - 14.4V at idle and under load (lights) about the same. So the alternator charges!!
Voltage between starter and battery earth = Voltage between alternator and battery earth = battery voltage.

Blue and Green Cable going from the alternator to ECU pins show less than 1.2 ohm resistance (between ECU and harness connecting to the alternator). I checked what was visible and they don't seem broken.

If I unplug the blue/green cable harness, idle goes back to normal, no more ups and downs.

I'm not exactly sure how or what to measure in regards to green/blue cable but:  

Voltage coming from green cable at the harness is always fluctuating at idle. Sometimes 11.2 Volts, sometimes 10V, sometimes 13V, but never over 13.8V. So this is a clue.

Blue cable has a low voltage. 0.2V or so. Manual says blue cable is responsible for transmitting a PMW signal to ECU to calculate electrical load on the alternator. So no idea how to test that.

If green cable is responsible for telling the alternator the voltage of the battery, then possibly this indicates the issue, since the voltage is always much lower than 14.2V and fluctuating.

So how do I know if the ECU sends the correct battery voltage to the alternator? And how do I know the ECU receives the correct battery voltage info.

I don't have extended knowledge about diodes and power distribution, but I traced the smallest cable on top of the positive terminal (most likely the one responsible for informing ECU about battery voltage). This cable goes into a diode+3 fuses attached to the outside ECU box. It's easy to spot as it's the only blob hanging around from the box. There are 4 terminals going into the diode. 2 of them show exactly the same voltage as the battery (12.6V engine off). the other 2 show 1-2 voltage less, but are not identical (one is less than the other). Also the red/white cable that apparently is supposed to tell the ECU the battery voltage shows less than the actual battery voltage (something similar to those 2 above).

If this means anything to anybody, or need more info, please let me know.

Thank you so much!

 

 

[TD4 P1190 Fuel Rail Pressure Plausibility]

On 9/19/2018 at 11:08 PM, Ally V8 said:

Sorry, my scopes are Pico 2 and 4 channel - bit much to do a single job. As much as I hate the parts shotgun, I think you might be better of in this case. I see Island 4x4 do a Bosch pressure reg for your car at £85+Vat.

Update: I decided to go for the O rings first. I have to 2 questions.

I couldn't find a thread that explains how to repair the pressure regulator valve for TD4, using the repair kit.

I managed to take the regulator out with hard work. I have the repair kit 2-O rings. green and white

I cant seem to be able to take the white O ring out of the regulator. It's very plastiky...not rubbery...

Question is how do I take it out and how do I put the new one in. The regulator filter at the tip of the regulator seem to be way bigger than the O ring diameter.

2 questions:
1. Any guides around on how to do it?
2. Any way to test the regulator functionality using a battery and a meter? I checked the regulator resistance and it's around 2.8 ohms.

I connected the regulator to 3.7V/ 7.2V and 10.4V batteries in this order. I could hear a click inside the regulator but can't see anything happening :))

I wanted to see if the diaphragm of the regulator is ok and not leaking, but it seems I can't really see that.

[TD4 P1190 Fuel Rail Pressure Plausibility]

6 hours ago, Ally V8 said:

Without a scope you are just guessing. As I see it you either need to find a decent garage that really does understand Bosch common rail ,(Fail as we call it) maybe even a dedicated Bosch fuel shop ?  Or you can just replace the regulator on the pump. From the symptoms you describe that is the most likely component. Unfortunately a multimeter is of very limited help with what you are diagnosing. Please use either OEM or genuine parts for these repairs,there are some horribly cheap and nasty parts on offer,these will either fail quickly or muddy the waters even more. 

 

can you recommend any inexpensive scope I can get?  Maybe on Amazon/ebay?

[TD4 P1190 Fuel Rail Pressure Plausibility]

On 9/13/2018 at 1:04 PM, Ally V8 said:

The better way to sort it is to use an oscilliscope,with this you would be able to see the duty cycle of the square wave of voltage applied to the regulator, plus the varying output from the rail sensor.With a decent scope you can then freeze frame the waveforms and see what pressure a duty cycle of say 70% on time produces as a pressure reading at a given rpm. 

Thanks for your answer. Unfortunately I don't have an oscilloscope. I've already tested the pressure sensor in terms of voltage and I get those voltages you mentioned.  But testing the pressure regulator is harder, especially because it's hard to reach.  Is there any other way to test the pressure regulator, without an oscilloscope? I have a multimeter and a diagnostic tool Icarsoft LRII , thats it. No graphs unfortunately. At most I can connect the multimeter to the regulator, but then...The issue occurs only under load (rarely if I just rev the engine stationary). So how can I test the regulator while driving?:D

 

The only two things left before blaming the HP pump are the pressure regulator and the throttle sensor.  The engine knock/limp and rattle happens not only when I accelerate but also when I release the pedal (sometimes abruptly) and never happens on idle. Also the pedal live readings are very random and don't always show a value based on input. Same goes for the regulator. Sometimes it goes to 4. Sometimes just to 2, under relatively same load. At idle is 0.71.  (Is it ampers or volts for pressure regulator current btw?)

Of course I cant exclude the pressure sensor itself.

But basically with pressure sensor disconnected: I understand why the P code/MIL doesnt come up....because the sensor generates it. What I don't understand is why the engine doesn't rattle or knock under load when it's unplugged. So far it seems the sensor generates that knock. It's either by sending mixed signals to regulator...orrr the regulator can't cope. Any other option?  

 

I still believe this is a very valuable clue. The fact that car doesn't choke if it doesn't know the value of the pressure means something is working at least. Can I know 100% something is not broken (HP Pump) just because car works without high pressure sensor?

Also I see the high fuel pressure values  oscillate alot. Even at idle....the pressure is never stable...they go up and down. 25-28k Kpa.   And under load, it's all over the place. But maybe that's not relevant.

I will try to disconnect the regulator itself and check the O rings as I've heard they go bad sometimes. Can I determine if it's faulty just by looking at it? I suspect the O rings will look normal. Obviously if they are broken I will see, however I doubt car would start if that's the case. If they look normal, I'll just put it back :))

 

 

 

[TD4 P1190 Fuel Rail Pressure Plausibility]

11 hours ago, Ally V8 said:

In my experience its usually a cabling or connector fault. Rarely the sensor itself.There is even a replacement overlay harness as a fix from LR.

I wish that was true. The harness was replaced already. The sensor gives readings and the fault P1190 is not about the sensor...it's about the pressure. When I disconnect the sensor I get P1191, which is the sensor itself. But...as I said, I wish it was just the cable. And tests should confirm the cables fault.. However, cables check OK for continuity and voltage.

One interesting thing though: The only thing I can do to avoid getting limps and MIL... is to disconnect the high pressure sensor. The car works fine without it. I mean as good as it gets without the sensor.

I don't just want to replace it based on an assumption. The sensor gives readings after all....

Also I suspect pressure regulator as a possible culprit. If pressure regulator controls the high pressure sensor in any way, or vice versa then, any of the two can be broken . Yesterday for example, I saw something unusual. Just before engine cut off in traffic as I was accelerating, pressure regulator current went to 4V. Then car died. Very unusual high current. The load was not that big.... Most times under high load regulator goes up to 2.5V... Maybe it was an effort to increase pressure.... So that makes high pressure pump faulty....

But then... why is car not limping when common rail sensor is disconnected...

[TD4 P1190 Fuel Rail Pressure Plausibility]

Hi guys!

Hippo needs rescue. Please help!

Freelander 2004, TD4, manual. 93k.

I keep getting the same code P1190- Fuel Rail Pressure Plausibility. Car starts limping usually in second and third gear around 2k revs +/-  

I tried many things already, cleared the code, but so far it keeps coming back when I go for a ride..... UNLESS I disconnect the fuel rail pressure sensor. Without the sensor connected the car doesn't limp anymore.

Code comes with MAF disconnected for example. Injectors are fine.

I do get live readings of 350+Kpa for LP and 26k+ at idle for HP pump, which goes up to 120k.

Can't go past 3k revs in 5th gear, 70MPH. Unless downhill.

I have videos if you need more evidence. But maybe you guys can explain why car doesn't go in MIL limp mode when fuel pressure sensor is disconnected. I checked the cables. They have 5v and 0.5v return at ignition. Can this mean 100% the sensor is broken?

 

Any help sooo much appreciated!! I've been dealing with this for some time and have no idea what can be wrong. And how can I test what is broken....