Is this a right-hand drive or left-hand drive car??

 

RHD UK car

 

On the ECM side, unclip the relays from the tabs and upend them. Find the relay with two white/green wires across from each other, and a white/blue and a black wire. That's the O2 heater relay. Swap it out and see what you get for voltage then.

You WILL NOT see both P1646 and P1647 at the same time. Once one of them is set, the system STOPS testing that circuit. Therefore it will never set the code for the additional side.

Cheers,

 

There is a little bright side..Reliant Robins can be beaten when cornering!

 

Additionally, get in the RH enclosure in front of the driver seat; find the ground stud in there with a bunch of wire lugs attached. Take it apart and clean up all the lugs etc., and re-secure it, just don't over-tighten it. That could be the cause of the 12v connected to the engine and 8v connected to the body.

Also, get under the car and find and clean up the ground strap from the body to the engine/trans assembly. It should be under a trans bellhousing bolt I think.

Cheers,

 

Reliant Robins usually end up on their roof when cornering,

Thanks again Steve for the info , much appreciated. Will have a go with the suggestions when I get home from work tomorrow . It's 00.39 hrs here in the UK so I had better get some sleep now.

I did run the engine with both the O2 sensors disconnected and was surprised to see both P 1646 & 1647 show on the Torque pro reader together. When I reconnected them both the P1646 disappeared but The P 1647 remained?

 

Been a bit tied up lately, (no not bondage) so haven't had a chance to look at the old jalopy yet.

Will try and get to it this weekend and follow through all the suggestions. I think I'll do the engine side first and take it from there.

I'd love to find out what's causing all this. With the faults being so varied and intermittent I don't know if I'll ever be sure if I've cured it or not.

 

Got a chance to look at the car today.

Started with the O2 heater relay. Couldn't find any with the colour of wires as specified, but did find one with 1x green/white, 1x green/brown, 1x white with a blue trace and 1 x green with a red stripe which I think is the heater relay? Changed this relay over anyway. Can't seem to find these colours on the wiring diagram.

There were a couple of earthing points under the relays so I cleaned and re-tightened these.

Went to the drivers side (RHD) enclosure and found the earthing point there, only 2 wires but again cleaned and retightened.

Undid the 13mm nut and removed the big connector on the bulkhead. Couldn't really see any corrosion but cleaned all the contacts anyway. Also found the other 13 pin connector, and cleaned this as well.

Haven't done the bell housing to body earth yet as couldn't get to it.

Re-connected the battery and started the car. No warning lights, no RP, no ABS, TRAC,nothing whatsoever. Connected the reader and the only fault showing was P1647 as pending.

Took the car for a drive, went like a rocket, with no sign of RP or any warnings .

Got back to the garage & turned the engine off. Re-started it and the RP light came back on. Checked the reader again and P1647 plus all the original injector codes were back, but at least all the non engine codes have gone for the moment, although the No Trac warning did flash briefly once.

Haven't had a chance to re-check the voltage at the O2 connector but I suspect that there is still a bad earth somewhere. I am a little confused by the colour codes on this sensor. Going into the sensor I have purple, green, white and white with a green trace. From the sensor I have 2 x black wires, 1 x white and 1 x blue. Which two wires should I get 12v from? On what I think is the heater relay the green and brown wire appears to have a permanent 12.57v going to it.

There has to be a bad connection somewhere as it is so intermittent although I am rather suspicious of the O2 sensor as P 1647 was the first code to show and has been there from the start. Could P1647 possibly trigger the injector codes or are they totally unrelated?

I presume none of the ABS, ASC or TRAC wiring goes through any of the connectors that I have cleaned so I am wondering what has made them suddenly go away?

Will try the engine body earth over the weekend but I am not too hopeful as to this being the problem.

 

Fig 04.04, and the colors are exactly as you say, so you are looking at a wrong diagram.

Please note that some issues/codes only trigger the check engine light after the 2nd drive cycle.

When looking at the drawing, I see only 1 relay, and the ECU is controlling the flow by pulling earth.

So if you have checked the cables end to end (from O2 sensor to ECU), and all is ok, you might just have a bad heater in the O2 sensor. Not sure how to check, maybe check the resistance of the working one and compare it. Just check Fig.04.04 for the correct cables.

 

I'm with the alternator also. That may not be the problem but it's sure the place to start. If the alternator is supposed to put out 14.8 volts and it's only putting out, let's say 11.8 volts, then ALL the voltage readings taken by your computer or even a code reader are going to turn up as faulty. Think about it. Your ECM reads all your cars sensors, maybe 30 or more, 387 times a second. It compares the readings with what it's programmed as the "correct" readings or at least in the correct range. Almost all the readings are voltages.
You send 14.8 volts to a perfectly operating temperature control sensor which, lets say has a nominal resistance of 330 ohm then you should get a voltage drop on the other side of the sensor. I'm not doing the math, it's not the point. The point is if you're starting with a variable that is different than the cars computer is programmed for you're going to get faulty codes.
Start there. If you have a volt meter put it on the battery with the car off. You should get about 12 volts. Let someone crank the car and the voltage should go up. Usually around 13-15 volts, depending on whether you're running the AC or other things, but you get the idea.

Hope this helps.

 

Checked the battery voltages again today. Multimeter across battery reads 12.32volts engine off and 14.35volts with engine running at fast tick over cold engine. I am sure that this is within the voltage parameters of ECU but of course does not mean that there aren't some low voltages somewhere in the circuit due to a bad connection.

 

All the ABS, ASC and TRAC warnings seem to be staying away at the moment. As Avos says the other issues only trigger the RP after the second cycle so for now I am being lazy and clearing the ECU before driving off and the car is running perfectly and goes like the wind.

Will have to finally find the real problem one day unless it magically just disappears in the same way it just suddenly appeared in the first place.

 

Don't get too excited I just wanted to test how to upload a picture. This is the multi pin plug attached to the bulkhead with a 13mm nut and held together with a 10mm bolt.

Cleaned this and my ABS , ASC and TRAC problems seemed to disappear, (coincidence?) but the dreaded RP remains!

 

Been away so no input.
It does seem to me the problem is the low voltage to the O2 sensor heater.
Just to clarify - you pulled the connector off the sensor and measured volts across heater +ve and ground, then across heater +ve and engine block?
If that's the case you've probably got a virtually open circuit on the heater ground so the heaters don't heat and you stay in open loop.
A meter draws only microscopic current so you can get some volts with a very poor ground. The heater, of course, draws a lot so you'll get no current flowing if the ground is bad.
What resistance do you get between heater ground and engine block?

 

Right now I'm inclined to think coincidence, but you never know, really, until you pin it down.

To continue Steve's point. The sensor heater voltage discrepancy is for sure one thing concrete that we should figure out. The best way to do that is really by testing voltage drop while the thing is in operation. That will require using something to backprobe the the two upstream sensor heaters. I say both, because we want to compare the two so the good one serves as a baseline, so we know what we should see on the bad one. I use "T" pins you can get at a fabric store, sometimes they call them basting pins. They can be pushed into the back of the connector terminals through the weather seals. See the pic, it shows one of the O2 sensor connectors at the back of the engine. Using the wiring diagram, find the wire that is the wire from the heaters to the ECM and slide a pin in each one. Then with the engine running, see what the voltage drop is at each one. It should be a rather low voltage, that's why we want to check the good one, too. If you find a high voltage drop, then that circuit is the one you need to trace for a bad wire or connection.

It would also be smart to move the "T" pins to the power side of the heater, just to verify you in fact have full battery, or charging system voltage, at each sensor heater.

Whew! Good luck!

 

Hi Steve good to have you back. Will have another check with the meter as I can't remember what readings I got from which wires and I must admit I am not 100% sure which wire is which as I think I had the wrong wiring diagram at some point.

On the sensor connector I seem to have a purple going to black, a green to white, a white to blue and a green and white tracer to black wire.

I have heard that the sensor has some sort of crystal in it and presume that the sort of voltage that a multi meter will send thru it to check the resistance can do it no harm?

I will check it out again soon and write down all the readings I get. I will definitely check the resistance to earth because as you say the earth may well only break down under load. I will write it all down this time and report back

Do you have any idea where the body earthing point is, that is shown to be in the alternator area at the front of the car more. I have found all the other earthing points shown but not this one.

Thanks for your continued interest in this annoying problem.

 

Thanks also to xjrguy .just seen your post too. I am going to make sure that I have the correct wiring diagrams and check out the the sensors as you say. I was definitely getting a higher voltage reading when using the block as an earth so the earth must be dropping out somewhere. I have tried so many different things now and it's all got a bit confusing so will start from scratch with these sensors and carefully note all the findings.

The ABS and TRAC warnings seem to be staying away but there obviously is still something not right with the wiring somewhere.

Once again many thanks its good to have some back up and support.

 

Have a look at the diagrams (contains priceless info), that wil not only tell how everything is connected, but also what sort of voltages/effects to expect.

Here is the part for the heater ground control : "GROUND (85 – 90% DUTY CYCLE AT IDLE)"

That suggests to me at least that you can expect different voltages, which maybe shows that what you measure is possible even ok, although I can't confirm that (maybe Xjrguy can confirm what the values must be).

Pending on the age of the O2 sensors, why not just change them both anyhow. If you still have an issue than at least you know there is one with the wiring of that specific O2 sensor.

 

André - where did you get that info ?
My JTIS shows the O2 heater grounded, not returning to the ECM so the volts should be the same across the plug as between feed and engine ground.

 

You must lookup the pdf that is specific for his year (which is the jyk2000en.pdf for his 2000 my car), for your 2004 car its already different.