Testing for a short to ground - 03 RHD Seville STS

[rockfangd]

that is what I was trying to explain.

I am thinking when you supplied power to that wire to the switch it blew the fuse because it is not  a 12v wire. It is very likely to be a ground.

Ground input, and ground output varying on the switch,

I suggest you unplug the switch, then check the input wire to it. Is it ground or 12v? with KOEO

With the switch unplugged will it blow the fuse??

These are 2 important things. 

Did you also read my last post regarding the other things that may be tied to the circuit

[rhdsts]

I'll have to admit I feel as though I am over my head with diagnosing this. I'll replace the booster and let you know how it goes.

Thanks for your help.

[OldCadTech]

10 hours ago, Logan said:

Update: But the rant continues. There are no magical PCM / BCM drivers or secret hidden ignition switch positions. Now they're talking about NO and NC relays...way off course...

The posts following this one prove my point....it truly seems as if they are making it up as they go....they cannot explain how the system relay works.  

11 hours ago, OldCadTech said:

Whether it is a normally open or normally closed switch makes diagnosis of a short to ground important. 

Logan is correct in the operation of the switch, but my point is, the switch is normally open unless the load is needed and then the circuit is energized, then the circuit opens back to a "normal" state.

So lets get off the dead horse and diagnose the problem rather than whether or not the diagram is correct.  The relay is normally open at high fluid pressure, which is the normal operating, non-energized condition.  When the pressure drops, the switch is closed the relay is energized and the pump runs, "builds pressure and the circuit opens again".

Mr Logan, as far as your rant is concerned, if this statement was directed at me, I can explain exactly how the system operates. Please PM me and I will explain it to you.

NO and NC relays and switches ( the PBPSwitch is a hydraulically controlled switch NOT electrical it only makes or breaks the circuit like a button ) are exactly the diagnostic point. If the pressure is high and the pressure switch is connected or ( closed ) then there will be a direct path to ground and the fused test will blow the fuse.

Mr Logan, In reference to your other rant about the PCM or BCM. The OP stated there was a key on pump test. I stated that if there was a key-on test regardless of the system pressure, then there would have to be another way to control the ground to energize the relay, possibly at splice 130.

11 hours ago, Logan said:

I consider key on as run.

How do you get key on engine off then?

So, with the horse, hopefully, now buried, the pump motor or the pressure switch can not be tested with the connector connected.

10 hours ago, Logan said:

The schematic is as clear as night and day...it is basic automotive electrical 101. A relay needs both power and ground. The current GM schematic for this system shows a open relay ground at the pressure switch. That, of course, cannot be correct. When folks can't read a schematic...we can tell.

ALL GM schematics show the circuit in a normal non-energized state, unless it is otherwise noted.  Again,  Mr Logan, PM me and I will help you with GM electrical schematics. I've been reading and understanding GM electrical schematics for a long time.

 

[OldCadTech]

@rhdsts ohm test the pump motor from terminals  C to B . Post what you have for resistance.

[OldCadTech]

@rhdsts discharge the booster pressure by applying the brake several times and test for continuity between terminals A and B, it should have continuity if it does not have continuity with the booster pressure discharged then the switch is defective.

[OldCadTech]

One more thing be sure to check the things that @rockfangd suggested as a lot of GM circuits share components. This is noted in the schematic where it references to check the power distribution

[rhdsts]

Thank you OldCadTech for your clear and concise suggestions. I am sorry if I have caused friction here, it was not my intention. It's 7.45pm here in Australia, so give it 14 hours or so and I should have some answers on those tests. Thank-you for your help, and your patience!

[OldCadTech]

No worries, you caused - No friction 

[OldCadTech]

Wait one,  I think I got the test written wrong it's 12:55am here. Yes I did, If the booster is discharged there should be continuity. Sorry about that I corrected the statement above also. 

[rhdsts]

19 minutes ago, OldCadTech said:

Wait one,  I think I got the test written wrong it's 12:55am here. Yes I did, If the booster is discharged there should be continuity. Sorry about that I corrected the statement above also. 

No worries! You've been really helpful - thanks. And go to bed  

[OldCadTech]

I was on the way to bed, then I thought - be sure to test the switch when the booster is fully charged or pressurized first, it should be an  open circuit. Again, make the tests with the connectors disconnected.

Okay, I'm going....

[rhdsts]

Okay I hooked up the pump, turned the ign to 'on' and the pump buzzed for maybe 20-30sec as it pressurised the fluid. Then I switched the ign off.

Then I removed the connections to the pump (two plugs: one for the pressure switch, the other for the pump motor)

I set the DMM to 200 Ohms (I hope that was the correct setting. Next one up was 20k Ohms, then 20M Ohms).

I tested terminals C and B (motor): 1.0 Ohms

Then A and B (switch) 0.9 Ohms.

Then for comparison, I tested the same pins on the new booster pump (out of the car, so no pressure stored)

C and B: 1.0 Ohms

A and B: 1.9 Ohms

Does any of that make sense?

rockfangd suggested looking at the other components that share the same 10A fuse. If the above resistance readings are within spec (did I even do the test correctly?) then the fault could lie elsewhere. 

When the fuse blew the first time, I got the following codes:

DTC P0102 Mass Air Flow (MAF) Sensor Circuit Low Frequency
DTC P0412 Secondary Air Injection (AIR) Solenoid Relay Control Circuit Bank 1
DTC P0418 Secondary Air Injection (AIR) Pump Relay Control Circuit Bank 1
DTC P0443 EVAP Purge Solenoid Valve 1 Control CKT

When I cleared the codes, replaced the fuse and drove around the block, only DTC P0102 Mass Air Flow (MAF) Sensor Circuit Low Frequency returned.

When I cleared that and had the car running in the garage (so no brake applications, and the booster pump only ran to get pressure to the correct level), there were no codes and the fuse did not blow.

 

EDIT: Just checked DTCs and DTC P0418 has appeared again. Cleared the code and ran the car without the booster connected (relay out) for 5min and then with it connected for 3-4min. No codes yet. Oh boy. What a headache I'm getting with this.

 

 

 

[rockfangd]

Did you read my post regarding the secondary air injection pump?

Assuming this car is a 2003 it should have the pump. They were very prone to failure and often sucked up debris and water.

It should be in the bumper on the driver side.

I asked this because it comes on when you start the car which is KOER (key on engine running). 

It does  not cycle on when the engine is not running. I mentioned it because you dont mention (that I saw) if the fuse blows with the key on engine not running.

No tension at all here .We all try to be professional,  Honest hard working fellows. Want to hear a good resolution here.

[rhdsts]

I think I have found the problem. The MAF sensor connector plug - wires are exposed and no doubt shorting out.

Any suggestions why this happened, and assuming I can buy a new plug, is it hard to swap out the wires?

 

 

[rhdsts]

Okay that's it - the MAF sensor wiring shorting out. The wires are in a protected spot under the air intake hose. The only thing that I can think of is that a couple weeks ago I replaced the A/C discharge hose. That runs from the compressor to the condensor, on the other side of the engine. To get the old one I had to pivot the hose towards the other side of the engine. I don't know how, but I must have got it caught up with the MAF wires. I was being super careful.

I feel like an idiot.

I'm glad I have a spare booster pump, as they are NLA new and hard to find used. They do fail. Still, I am glad that I did not go ahead and replace the pump.

Thanks guys for all your help. I am sorry that I wasted your time.

[OldCadTech]

@rhdsts

You shouldn't feel bad at all, and you didn't waste anyones time.

Thursdays are a late night for me, so a little delay in getting back to you. To me it looks a lot like rodent damage. Do you have rodents in Australia? You know the small ones, not the ones with the big feet.. JK  

You did good, congratulations, fine job! I love a happy ending. Those connectors are easy to find, at least they are here anyway. There is a special tool to get the wire out of the connector and another special crimp tool as well. Not very expensive tools. 

[rhdsts]

39 minutes ago, OldCadTech said:

@rhdsts

You shouldn't feel bad at all, and you didn't waste anyones time.

Thursdays are a late night for me, so a little delay in getting back to you. To me it looks a lot like rodent damage. Do you have rodents in Australia? You know the small ones, not the ones with the big feet.. JK  

You did good, congratulations, fine job! I love a happy ending. Those connectors are easy to find, at least they are here anyway. There is a special tool to get the wire out of the connector and another special crimp tool as well. Not very expensive tools. 

We do get rodents here, plenty of them. It could be that a rat got in there, but the problems started not long after I replaced the A/C discharge hose. It was leaking at the rubber section of the line. Either when removing it or replacing it, I might have got the line caught up with the MAF wires. I do remember having to jiggle it around a lot to get it out - it's pretty tight in there - but I was not in a hurry and thought I was being careful. I think I was focussing too much on where the line was jamming up near the right-hand headlight to worry about what was happening with the othr end of the line. I thought that that end of line was right up close to the cylinder head when I was angling it to get it out, but maybe not. 

I have soldered the badly damaged black wire (which was down to a couple threads) and used hot glue to insulate around it, then insulating tape. I will order a new connector from Rock Auto, which comes with pigtail wires on it so I can just cut the old plug off and solder the wires to the new plug's pigtails. If course I will use heat-shrink tubing and insulation tape as well. I don't plan on revisiting this...

The car was actually playing up before the brakes went. It used more fuel than it should and lacked performance on occasion when I went on a 300km round trip a few weeks ago. That plus a hesitiation randomly occuring - well, it all goes back to those MAF wires.

Well, at least we all learned quite a lot about the RHD Seville brake booster!

[OldCadTech]

1 hour ago, rhdsts said:

Well, at least we all learned quite a lot about the RHD Seville brake booster!

Yes we did, thank you

Kudos to @rockfangd he was definitely on track, good call. 

[rockfangd]

glad to hear you figured it out. It is crucial to be positive of a failed component before replacing it. 

It looks like rodent to me also. Could be wrong though. Look in the area below that plug and see if there is anything piled

[rhdsts]

4 hours ago, rockfangd said:

glad to hear you figured it out. It is crucial to be positive of a failed component before replacing it. 

It looks like rodent to me also. Could be wrong though. Look in the area below that plug and see if there is anything piled

I checked and it's pretty clean under there. Bad luck really, it looks like the A/C pipe I replaced got caught up with the MAF wires. Just shows it pays to be super careful when replacing parts like that I guess.

I soldered the black wire at the back of the plug as it was down to a few strands of wire. I'm helping my daughter with a project (she's making a USB phone charger for her brother for Xmas) and the on the Youtube videl the guy used hot glue to insulate some hard to get to wires.

So I used hot glue around the soldered wire on the MAF wiring, then wrapped all with insulation tape. Even without the glue I don't think it could touch the red wire (which it was before, thus blowing the fuse) as I insulated that section of the red wire.

Given the heat under the hood, was it a bad idea to use hot glue?

I will get a replacement plug which comes with an inch or two of wires. Until then, do you think my fix will stop a short?

 

[rockfangd]

should be just fine.

I would get a donor pigtail and solder it in with heat shrink tubing too cover the solder joint

Keep us posted

[OldCadTech]

What rock said X2

[OldCadTech]

A little trick I use so the solder points don't end up in a clump is to stagger the solder joints a little, That way the wires fit back into the wire conduit a LOT better.

[rhdsts]

21 hours ago, OldCadTech said:

A little trick I use so the solder points don't end up in a clump is to stagger the solder joints a little, That way the wires fit back into the wire conduit a LOT better.

Great idea - thanks!