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ABS Code 15 RR sensor open/short; ABS Control Unit Location


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#1 Ian_D

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Posted 22 July 2019 - 11:48 AM

 2001 Accord 2.3 Type V RHD

Can anyone help with the ABS control unit location and/or ABS fault code 15: Wheel sensor (open/short to power) RR?

In detail:

After an intermittent ABS warning light that always went out before I could investigate, it is now on permanently.  Shorting the required connector and reading the blinks gives me ABS fault code 15: Wheel sensor (open/short to power) RR.  

 

I'm working from the US Accord service and wiring manuals.

 

My first suspects were the sensor and the connector at the wheel.  However, the sensor gives the same resistance as the others and the connector and its terminals are in good condition with no sign of water or dirt ingress.   All the voltages and resistances on both sides of the connector at the wheels are similar to those at the RL wheel; disconnecting the RL wheel gives code 17 as expected and reconnecting removes it.  I could splice the wires to by pass the connector or cut through the sleeving to check the connector but I'm wary of causing new problems.  

 

I'm banging my head against a brick wall on finding the ABS Control Module so that I can check at that end.The US Service Manual gives the control unit location as the left-hand kick panel (where our RHD passenger's foot would be) but it's not there.  I've taken off both kick panels, the centre console and the lower dash panels but can't find it'  The ABS pump module and wheel sensor wires from the sensors quickly disappear into the looms so are no help.  I've taken a mirror and torch to look as far under the dash as I can.  Still no control unit.

 

As for the fault itself, my first suspect was the connector at the wheel.  However, its terminals are in good condition. There is no sign of water or dirt ingress.  I could splice the wires to by pass the connector or cut through the sleeving to check the connector but I'm wary of causing new problems.  I'd rather check at the control unit first.

 



#2 HONDALEO

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Posted 22 July 2019 - 03:06 PM

I have a 1999 Accord and a 2005 Accord.

They both use entirely different systems, so I'm not sure what year the change took place.

The 1999  car uses an analogue sensor, i.e. it produces a sine wave.

The 2005 car uses a digital sensor.

 

If your car uses the analogue sensor then you can test the output using a multimeter set to display Volts AC

You can then compare RR to RL (you can do this in two scenarios, 1) with the connector connected, and 2) with it disconnected)

 

Depending on the outcome of those various tests, you can determine if the sensor is the problem, or if it is a loom problem, between the sensor and the module.

 

(i.e. if the sensors bad, it wil always be bad. If the loom is bad, the sensor will appear good when the loom isn't involved)

 

It might take quite a bit of wheel rpm to get a decent reading, and keep in mind that the multimeter only samples periodically, so the faster and more consistent you can make the wheel speed for testing the better.

 

(If you have an oscilloscope the speed isn't so crucial to capture the data).

 

I'm guessing your car uses the analogue sensor, so I will no go into how to test the digital one just yet.

If you are convinced it is digital, I have a powerpoint I can send you, which I created last year when I did lots of tests to understand how the digital system operated.



#3 Ian_D

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Posted 22 July 2019 - 07:21 PM

Thanks.

 

AFAIK it's analogue so I could check that.  However, there are separate fault codes for wheel sensor pulses that I assume would be used for that failure, not the open/short to power that I have.

 

I have, though, just ordered a new pattern sensor as they're pretty cheap, less than £10, which gives me the option of changing the sensor if the old one has broken or there is an incompatibility with the connectors.



#4 HONDALEO

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Posted 22 July 2019 - 08:26 PM

I'm pretty sure If you unplug the connector, then switch the ignition on, on one the two wires coming from the module, there will be about 4.8V.

The module uses this to test the sensor circuit integrity, even before a wheel turns.

(With the connector connected, the sensor will pull this voltage down to about 0.15V)

 

If you have the sensor unplugged,you should still get this same code if the wire is shorted upstream of the sensor. (and also the 4.8V won't be measurable as ought to be as stated above).

If this is true, then both sensors should produce the same AC voltage when unplugged and the wheel is rotated, i.e. if both sensor are not faulty.

 

If the short is inside the sensor, then you should get an open circuit fault code with the sensor unplugged.

I think you can determine the fault by this elimination process, and learn something about how the system works,

But if you just want it fixed and you can maybe do it for less than £10 then it's no big loss to give it a go.

 

If it doesn't work, at least you'll have a spare sensor :-)


Edited by HONDALEO, 22 July 2019 - 09:08 PM.


#5 Ian_D

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Posted 23 July 2019 - 08:42 AM

Thanks.

I'd discounted a short to power. The first step on the DTC fault-finding is to disconnect connector 22P at the control unit and measure the + wire's voltage to earth; if it's more than 2v then repair the short to power, if not then carry on fault-finding.  My best interpretation of this was to check at both ends of the sensor connector, which gave around 0.15V (one of your 2 figures) at the control unit end of the + wire, nothing at the - wire and nothing at the sensor end (as expected from a disconnected sensor); I got the same at the RL wheel.



#6 HONDALEO

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Posted 23 July 2019 - 03:42 PM

Sorry, I find your description a bit confusing. All I can say is mine works fine and below is shown the voltages I measure with the ignition switch on.2m5ihi9.jpg


Edited by HONDALEO, 23 July 2019 - 06:52 PM.


#7 Ian_D

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Posted 23 July 2019 - 10:43 PM

Again, thanks.

 

Measured at the sensor connector the voltages to earth with ignition on and the sensor disconnected are 0.15v for your red wire (Green/Yellow , RRW(+), from pin 19 according to the manual), not the 4.8v that you show, and 0V for your blue wire (Blue/Yellow , RRW(-), from pin 20 according to the manual).

 

I get these same voltages at the equivalent wires of the Rear Left wheel sensor circuit that gives no fault codes.

 

The manual states:

1. Disconnect the ABS control unit connector A (22P).

2. Start the engine.

3. Measure the voltage between the appropriate wheel sensor (+) circuit terminal and body ground.

Is there 2 V or more?

Yes - Repair short to power . . . 

No - Go to Step 4 . . . 

 

At the end of the day I really want to find the control unit so that I can check from there iaw the manual (successively check voltages at the control unit connector, then resistances at the control unit connector for: RRW+ to earth (should be open circuit); RRW- to earth (should be open circuit); and RRW+ to RRW- (should be 450 to 2000 ohm). If no-one here can direct me to it then I'll have to, in order: connect the new sensor; then, if that doesn't sort it, check resistances through the sensor connector; then follow the loom from the sensors, whichever is easiest.

 

This is the sort of thing that I hope to see: https://www.ebay.co....QMAAOSwfVpYv9G3


Edited by Ian_D, 23 July 2019 - 10:46 PM.


#8 HONDALEO

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Posted 24 July 2019 - 02:01 AM

I'm afraid I don't know the modulator whereabouts on your car, but on mine it is right under my nose, right beside the power steering pump.

 

28ja41w.jpg



#9 Ian_D

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Posted 24 July 2019 - 07:49 AM

Thanks again.

 

My modulator is in the same place, but that isn't what I'm looking for. 

 

That diagram doesn't show an ABS CU, which surprises me.  Perhaps it's combined with or mislabelled as the driver's fuse/relay box.

 

I've tried to post images and pdfs but I can't seem to do so without first uploading from my hard drive to a site to get URLs, and mine is playing up.  The best I can get for now is the whole manual at http://www.gvrdeu.or...a Accord SM.pdf

The ABS system is on P19-35 (863 of 1695) onwards.  The location image is at P19-36 (864 of 1695) and DTC15 fault finding at P19-52 (880 of 1695).



#10 HONDALEO

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Posted 24 July 2019 - 12:14 PM

Since, like you said, you are using the wrong manual, maybe your ABS unit is in the same place as mine:-

15e8t5h.jpg



#11 Ian_D

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Posted 24 July 2019 - 02:21 PM

Thanks.  I suspect you're right.  I had thought of that, but searches on my ABS modulator's number came up only with an eBay listing for a Carina modulator and separate CU, and without a wiring diagram for the moulded plug I wouldn't be any further further forward.

 

My new sensor arrived and I quickly plugged it in.  Lo and behold, the ABS light disappeared. That is the last step in the fault finding process with the results that I got.  Getting out the old sensor is easier said than done though . . . . . 

 

This may be useful for someone else who has the problem, with your info on voltages and a combined modulator and my links to a manual with the fault finding.

 

Once again. Thanks for your help, I appreciate it.



#12 HONDALEO

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Posted 24 July 2019 - 02:39 PM

That's great.

The only thing is I am now baffled why mine reads 4.8V :huh:

It's working anyway, so hopefully I never need to find out!



#13 Ian_D

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Posted 26 July 2019 - 08:47 AM

Aargh.  It's back.  So it looks as if I'll be investigating the wiring from the modulator assembly after all.

 

I've just ordered from eBay a UK service manual on disc and hopefully that will have the info I need.


Edited by Ian_D, 26 July 2019 - 10:00 AM.


#14 Ian_D

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Posted 28 July 2019 - 07:25 AM

After a day with several trips where the ABS light stayed on I've now had 2 days with several trips where the light has been off.  I can't do any further fault finding.

 

The car definitely has a Gremlin taken up residence.



#15 Channel Hopper

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Posted 28 July 2019 - 10:29 AM

On the Mk7s the ABS warning light can come on owing to a damaged pulsing ring which is part of the wheel assembly. 

I chose to burn out the rotten sensor since others had damaged the ring by using a drill.



#16 Ian_D

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Posted 29 July 2019 - 06:41 PM

Thanks.  I think that's not the problem as it should generate a different fault code (the one I have covers an open or short circuit).

 

The ABS light was back on today.  That gremlin is having fun.

 

US cars route the RRW sensor through the right-hand under-dash fusebox, generating 2 connectors and an additional connector on top of that.  I suspect we have extra connectors too and that these are causing the problem.

 

My manual should have been here on Saturday but isn't here yet :-(



#17 Ian_D

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Posted 30 July 2019 - 07:21 PM

The Gremlin is still having fun putting the light on and off.

 

My manual has arrived.  It shows no CU and includes a wiring diagram for fault finding from the modulator connector, suggesting the CU is in the modulator.  Now I just have to wait until the light comes on and then find out how to remove the connector. . . .



#18 Ian_D

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Posted 03 August 2019 - 08:36 AM

Now sorted, I hope.
 
Checking the resistances of the wires showed that the +ve to the sensor had a high resistance of ~15k between the modulator and the sensor connector. Unfortunately I could find neither connector nor wire routing and location diagrams in the ESM so had to trace the wires manually, which was a PITA because they disappeared into the tangled mass of looms, connectors and blocks in the lower dash/kick panel by the driver's right foot. 
 
By checking continuity whilst disconnecting each connector I could get access to and disconnect with less than 2 swear words, eventually I found that the wires went through the driver's dash fuse box housing (as you look from the outside, the +ve to the wheel sensor is the second green/black wire down on the top left green connector).  The resistances to the sensor were fine, suggesting that the problem lay in the wires between the modulator and fuse box housing. The warning light went out after I rummaged around in the rats nest of wires, suggesting that the connector at the other side of the fuse box housing had a dodgy connection, probably affected by the leads from an aftermarket stereo to the door speakers.  I decided to reroute the leads and leave the rest alone, fearing that disturbing tightly-packed wiring to get access to the connector concerned would cause more hassle than it was worth.
 
If any has this problem then they're welcome to message me for the ESM sections.


#19 Channel Hopper

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Posted 04 August 2019 - 08:20 PM

Is the original ABS fault fixed ?