Toyota / Cobra Parking Sensor Control Module Fault

[Wilksey]

Hi,
FYI I have ordered a 2nd hand unit as I have no idea about these boxes.

Anyways, I have a parking control module that just beeps continuously, started happening one day out of the blue, I unplugged all of the parking sensors and it just kept beeping still, I removed the unit from the car and popped it on my bench for further inspection.

Seems to be 4 x circuits with transistors and some kind of inductor / transformer and some misc circuitry for power and buzzer.

I hooked it up to a 12V bench supply, the 4 x sensor inputs all appear to be connected to ground, two pins per input, not sure if this is correct??  Seems connected to GND with power on or off, not hooked it up to a scope so not sure if it is generating any signal (40KHz for Ultrasonics?)  all 4 seem the same so I guess this is correct operation?

The buzzer output has a permanent connection to ~12V so is always on, none of the transistors seem shorted, not inspected it that closely, done some basic probing.

I presumed that with nothing connected it should be silent - or so the forums suggest.

The unit is a Toyota branded Cobra unit 4m0168T1A, or Cobra part code 4m0168a1c.

I can find posts with the same issues and the end result is change the control unit, but not much on how to fix or what might be wrong.

So, if anyone has any information on a possible fix for these things then do please tell, can't find any useful information about it.

I've seen one image with coloured splodges on the 3 electrolytic caps and the 4 x EPCOS branded inductors / transformers, all 4 outputs seem to buzz out the same and seem to give the same output, the caps measure OK.

I could hear a slight fluctuation in the tone when plugged into the sensors and covering it, but the constant buzz saturated it so not sure if the output is shorted on, or if there is a logic fault.

I can take a picture of the circuit board if it helps?
EDIT: https://ibb.co/0yPbJVT
Image of board.

TIA!

[fzabkar]

Would you have the pinouts for the connectors?

I don't know anything about these devices, so would you be able to explain how the control unit works? I see that there are 4 x 2-pin sensors. Presumably these are the outputs for the ultrasonic transmitters. So where is/are the ultrasonic receiver/s? I presume the transmitters are mounted on the rear bumper.

Some datasheets …

http://www.ti.com/lit/ds/symlink/lmc6035.pdf
www.ti.com/lit/ds/symlink/sn74hc4066.pdf
http://pdf.datasheetcatalog.com/datasheet/fairchild/FM93C56.pdf

[Wilksey]

Hi,

Thanks, I tried peeling the sticker off the other chip, presume it's a micro, but it left most of the white backing behind so will need to try and clean it off to see what it is.

Yes the 4 x 2 pin connectors on the right of the pic are the transducer inputs which are mounted in the bumper, the larger 4 pin connector to the right of these is power, only 2 pins used, not sure what the other 2 are for, the 2 pin to the right of that is the buzzer output.

I can't find anything on the EPCOS devices.

I am presuming from what I have read that the control unit produces a 40KHz signal that it measures the time to return on the transducer and works out the distance based on the reading.

There appears to be 4 single op amps, an analog switch and an e2, and presumably the sticker covered chip is a micro.

The circuitry around the transformers seem to be duplicated 4 x, so I guess that is the signal generation and receive for the transducers which is then fed into an opamp and the buzzer driven by some transistor arrangement from the micro.

So I guess it could be either faulty transistors, faulty input or faulty micro.

I've probed around the transducer inputs and they all seem to be the same, if I probe between the 2 pin inputs both pins are essentially connected to ground, which might be their idle state?

I don't know too much about ultrasonics, just some basics and working with the SR04 module which has a transmit and receive transducer and the circuity already on-board.

Cheers

[longboard1210]

having worked on these for years the conectors on the sensors corrode inspect he wiring first the main units are pretty reliable

[Wilksey]

I think it is the main unit because when I disconnect all sensors from the main unit it just emits a continuous beep.  According to the Toyota forums the unit should not make any noise with the sensors disconnected.  I believe the main unit is a "common fault" but people just replace it rather than repair it, so I'd be interested to find a way to repair it if possible.

[fzabkar]

I still can't see how a 2-pin connector can support both an ultrasonic transmitter and a receiver

I'm curious about the identity of the micro and the PSU ICs near the capacitors. Can you provide some marking info?

More datasheets ...

SZBZX84C5V1LT1G, ON Semiconductor, 5.1V Zener, 225mW, marking Z2, SOT-23:
http://www.s-manuals.com/pdf/datasheet/b/z/bzx84bxxxlt1g%2C_bzx84cxxxlt1g%2C_szbzx84bxxxlt1g%2C_szbzx84cxxxlt1g_on.pdf

BCW66GLT1G, ON Semiconductor, NPN general purpose BJT, 45V, 800mA, 225mW, marking EG, SOT-23:
http://www.s-manuals.com/pdf/datasheet/b/c/bcw66glt1%2C_sbcw66glt1_on.pdf

BCW33LT1G, ON Semiconductor, NPN general purpose BJT, 32V, 100mA, 225mW, marking D3, SOT-23:
https://www.onsemi.com/pub/Collateral/BCW33LT1-D.PDF

BAV99LT1G, ON Semiconductor, dual series switching diode, 100V, 215mA, 225mW, marking A7, SOT-23:
http://www.s-manuals.com/pdf/datasheet/b/a/bav99l%2C_sbav99l_r11_on.pdf


TDK/Epcos has only one type of off-the-shelf transformer for "ultrasonic park assist":
https://www.tdk-electronics.tdk.com/en/1110696/products/product-catalog/transformers/automotive-transformers-for-ultrasonic-sensors--epcos-
https://en.tdk.eu/inf/85/ds/B78416A2232A003.pdf

ISTM that the A1607 transformer must be a custom part.

Elmos apparently produces designs in collaboration with TDK/Epcos:
https://www.elmos.com/english/products/sensors/ultrasonic-distance.html

Elmos manufactures Digital Ultrasonic Transducer Driver and Signal Processor and Sensor ICs with 2-wire and 3-wire interfaces ("IO pt-to-pt Interface"). This interface is the communication path between the IC and an external host ECU. The transducer appears to combine the transmitter and receiver in a single package with a 2-pin connector.

https://www.elmos.com/fileadmin/elmos-website/products/sensors/ultrasonic/elmos-digital-ultrasonic-transducer-driver-and-signal-processor-e52402-is.pdf
https://www.elmos.com/fileadmin/elmos-website/products/sensors/ultrasonic/elmos-2nd-generation-ultrasonic-transducer-driver-signal-processor-e52408-09-is.pdf


LMC6035IM, Texas Instruments, dual RRO op amp, 2.0V - 15.5V, SOIC-8:
http://www.ti.com/lit/ds/symlink/lmc6035.pdf

HCF4066, STMicroelectronics, QUAD BILATERAL SWITCH FOR TRANSMISSION OR MULTIPLEXING OF ANALOG OR DIGITAL SIGNALS, SOP-14:
https://www.st.com/resource/en/datasheet/cd00000388.pdf
http://www.ti.com/lit/ds/symlink/sn74hc4066.pdf

FM93C56, Fairchild, 2048 bit serial EEPROM, 2.7V - 5.5V, SO-8:
http://pdf.datasheetcatalog.com/datasheet/fairchild/FM93C56.pdf

TDK/Epcos has only one type of off-the-shelf transformer for "ultrasonic park assist":
https://www.tdk-electronics.tdk.com/en/1110696/products/product-catalog/transformers/automotive-transformers-for-ultrasonic-sensors--epcos-
https://en.tdk.eu/inf/85/ds/B78416A2232A003.pdf

[Armadillo]

I see that you guys are pretty serious at troubleshooting, so allow me to chip in my 5 cents;     

See attached;

I suspect the output transistor or IC is shorted and power through to buzzer.

Suggestion: Find the First Component using Stone Age technique;
Multimeter in buzzer mode, one probe to the pin arrowed in RED, one probe goes thru all the component leads to identify the first connection component with a 0000 reading. [buzzer sound does not mean is zero reading].
This  identify the area to focus on. Then blow close up on that area and post up.

[fzabkar]

Both transistors in the vicinity of the buzzer connector are NPN BJTs. If the transistor driver were shorted, shouldn't we be looking for a short from BZ- to ground rather than a short between 12V and BZ+ ?

[Armadillo]

Should be feasible, but best he identify the first point so that you can be more certain of the output point.

Hope its the output problem, otherwise would be the common echo reception/detection hang High, which would be more difficult to communicate thru in troubleshooting.

[longboard1210]

So i take it you have tested the sensors while the unit is powered? by holding your finger on the sensor when its on
They should all click with light finger pressure

Ive worked for toyota fo 16+ years so have a bit of in house know how

[Wilksey]

Hi,
Thanks for your responses, i'll do some more probing of the unit next week, I left it in work, and try and identify the micro.

I suspected a shorted transistor, or something similar, I am not sure if it switches + or - to the buzzer.

I don't know how it works in terms of only having 2 pins, I presume it generates the signal, sends a signal out, then somehow turns the transducer around into receive mode and listens for the echo back, I presume there is a finite amount of time to do this, not sure what the minimum time is for the ultrasonics to return an echo, of course I could be completely wrong as I don't know 100% just guessing.

@longboard1210 - In short yes and no, I can hear them changing the signal when plugged into the control unit, but the main beep saturates the audio, so they are definitely being picked up and doing something, I have a second hand control unit and some more sensors on the way so I can test different things.  The car is a UK Avensis T25 T-Spirit estate, 2.2 diesel, and it is branded as "Delta elettronica S.p.a", but it is the same as the Cobra branded units, the front and back control units have the same code 020336 written on them, mine doesn't have front ones, so I can't swap them over unfortunately.


Cheers!

[fzabkar]

FWIW, the attached diagram helps me to understand the sensor function.

[Armadillo]

There are also these ingenious designers out there with their clever tricks at watchdog reset circuit implementation that never fails to astonish.

Wild guess but it would be wise to firstly check that the ucontroller is alive and ticking, so to speak before spend time uncovering the circuit further.   

It would be logical to think that if the ucontroller is dead, the buzzer will sound to inform the driver this "Hey!, dude, you are on your own".

A close up on the ICs would be educational. 

[longboard1210]

Yes yours is the tpa 400 kit
Its not audio you are listening for
put the car in reverse and physicly feel the top of the sensor it will click when you lightly put your finger over it you will feel it you should get this result on all of them
you will find one or more not working thats what the long beep means
if you remove the sensor it has a small connector that gets water inside it and corrodes the pins

[Wilksey]

Hi,
I'll do some more checks on the controller and see if I can uncover the IC.

@longboard1210
- Oh, no I haven't physically touched the sensors, I did check the pins for corrosion when I disconnected them from the unit and they all seem OK.
I'll do some more investigating when the new controller arrives because it is a pain in the arse trying to remove the rear boot trim to get to where the cables are.
I have some more sensors on order so I can try different sensors, I will try connecting the sensors up to the original controller on the bench.

Have you worked with these on an electrical level before?  Is it supposed to beep constantly when no sensors are plugged in, forums suggest it is supposed to be silent with nothing plugged in?  Is there a "common fault" for these units as it seems a lot of folk have the same issue?


Cheers

[longboard1210]

sensor connectors are on the sensors behind the bumper in all the weather hence the corrsion problems

Worked on loads with no sensors connected gives out a no connect fault beep

Yes common fault is corrosion on the sensors and wiring the ecu realy go down unless they have water ingress

[fzabkar]

PARKING CORNER SENSOR TROUBLESHOOTING • WIRING DIAGRAM MANUAL:
https://www.toyota-tech.eu/aimuploads/%7B3BD54442-C0E2-AA9F-5E05-522A1610C0E2%7D/07%20PCS%20Diagnose%20Manual.pdf

[Wilksey]

Thanks, I don't know if the fault is the same, just a continuous drone from the rear end, my sensor controller doesn't look like that, just has the 4 inputs and power and speaker.

I have been told that my parcel (new second hand parking sensor controller) will be here next week some time.  Bit later than originally stated but whatever as long as it arrives!

[Wilksey]

Update,
New control unit fitted and it all works perfectly, so defiantly the control unit, i'll try and get around to probing the old one soon and see if I can do a further analysis.

Cheers

[Wilksey]

So I managed to clean up the board  a little bit today and take some close up photos, if anyone wants to see them let me know as they are around 85MB so i'll have to zip them up and pack them off to a file host site.

Here is one of interest though:
https://ibb.co/k393fGH

The MCU is a Freescale / Motorola mc68hc908jl3e

Which looks like an 8 bit MCU.
Next to that is a chip labelled 4269G, which looks like a 150mA 5V LDO.

Cheers

[fzabkar]

I'd be interested in seeing the photos. I can see how the 4066 switch works, so that would be one place to trace the US signals.

NCV4269, ON Semiconductor, 5.0V, 150mA LDO regulator, SO-8:
https://www.onsemi.com/pub/Collateral/NCV4269-D.PDF

MC68HC908JL3E, Freescale / Motorola, 8-bit MCU, 4KB flash, LVI, ADC, 3V/5V, PDIP-28:
https://www.nxp.com/files-static/microcontrollers/doc/data_sheet/MC68HC908JL3E.pdf

[Wilksey]

Hi Res photos uploaded as a ZIP to Zippyshare.
https://www89.zippyshare.com/v/ROkRvGDS/file.html