ABS sensor testing... please help !
- Thread starter jonmig
- Start date
found this on a google search, it'll give you some Idea how to do it !
UNDERSTAND WHEEL SPEED SENSORS:
Note: The wheel speed sensors are two-wire hall effect transducers which send a digital square wave signal with a low of .75 volts and a high of 2.5 volts to the DSC control unit. Each sensor receives a well-regulated 8 volt power supply from the control module through one wire. The ground path for the sensor is through the second wire back to the control module. The signal is generated by a pulse wheel affecting the voltage flow through the hall element in the sensor. The pulse wheel is integrated into the wheel bearing assembly, behind the seal. This protects the trigger wheel from foreign substances which may affect the wheel speed signal.
TEST WHEEL SENSOR CIRCUIT FROM THE ABS CONNECTOR (also checks wiring circuit):
OPTIONAL: Jack car up (so that all four wheels can be spun to test voltage & resistance fluctuations of the hall-effect sensors)
- Turn the car off and remove the key from the ignition.
- TEST 1: Switch the DMM into the diode test position
- Wrap a stiff 20AWG wire onto the ends of your DMM probe for sticking into ABS-connector pins
- Label the positive 20AWG wire with white tape so that you won't get confused as you switch back and forth
- Stick the ends of the wire into the appropriate female holes of the ABS connector (13-29, 30-31, 28-12, 15-16)
- In one direction, you should see 1.7 to 1.8 volts (note the pinouts mentioned are in order, positive to negative)
- In the other direction, you should see OL or some other infinite reading (open circuit)
- TEST 2: Switch the DMM into resistance checking mode (optional)
- You should see around 3.3 Mega ohms in one direction & approximately twice that in the other direction (but some say more)
- TEST 3: If desired spin the wheel at about 1 revolution per second, by hand (the resistance should fluctuate as the wheel spins)
- TEST 4: Switch the DMM into millivolt mode (optional) & again spin the tire & wheel assembly by hand (test-lead polarity won't matter)
- You should read between 1 and 5 mV when you spin the hub (no voltage implicate the sensor or circuit)
- OPTIONAL TESTS BELOW REQUIRE FLYING LEADS WITH THE IGNITION SYSTEM ABS SYSTEM CONNECTED & POWERED UP:
- TEST 5: Swith the DMM into the 10v and attach flying leads to the sensors with the power on
- You should see the voltage going to the sensor and the return signal
- Expect a baseline voltage of about +5 to +12 volts depending on the ABS system (does anyone know this value?)
- Expect that baseline voltage to the sensor to change (by how much?) as you spin the wheels
- TEST 6: Hook an oscilloscope with "flying leads" to the ABS sensors (notice that the ABS system must be powered)
UNDERSTAND WHEEL SPEED SENSORS:
Note: The wheel speed sensors are two-wire hall effect transducers which send a digital square wave signal with a low of .75 volts and a high of 2.5 volts to the DSC control unit. Each sensor receives a well-regulated 8 volt power supply from the control module through one wire. The ground path for the sensor is through the second wire back to the control module. The signal is generated by a pulse wheel affecting the voltage flow through the hall element in the sensor. The pulse wheel is integrated into the wheel bearing assembly, behind the seal. This protects the trigger wheel from foreign substances which may affect the wheel speed signal.
TEST WHEEL SENSOR CIRCUIT FROM THE ABS CONNECTOR (also checks wiring circuit):
OPTIONAL: Jack car up (so that all four wheels can be spun to test voltage & resistance fluctuations of the hall-effect sensors)
- Turn the car off and remove the key from the ignition.
- TEST 1: Switch the DMM into the diode test position
- Wrap a stiff 20AWG wire onto the ends of your DMM probe for sticking into ABS-connector pins
- Label the positive 20AWG wire with white tape so that you won't get confused as you switch back and forth
- Stick the ends of the wire into the appropriate female holes of the ABS connector (13-29, 30-31, 28-12, 15-16)
- In one direction, you should see 1.7 to 1.8 volts (note the pinouts mentioned are in order, positive to negative)
- In the other direction, you should see OL or some other infinite reading (open circuit)
- TEST 2: Switch the DMM into resistance checking mode (optional)
- You should see around 3.3 Mega ohms in one direction & approximately twice that in the other direction (but some say more)
- TEST 3: If desired spin the wheel at about 1 revolution per second, by hand (the resistance should fluctuate as the wheel spins)
- TEST 4: Switch the DMM into millivolt mode (optional) & again spin the tire & wheel assembly by hand (test-lead polarity won't matter)
- You should read between 1 and 5 mV when you spin the hub (no voltage implicate the sensor or circuit)
- OPTIONAL TESTS BELOW REQUIRE FLYING LEADS WITH THE IGNITION SYSTEM ABS SYSTEM CONNECTED & POWERED UP:
- TEST 5: Swith the DMM into the 10v and attach flying leads to the sensors with the power on
- You should see the voltage going to the sensor and the return signal
- Expect a baseline voltage of about +5 to +12 volts depending on the ABS system (does anyone know this value?)
- Expect that baseline voltage to the sensor to change (by how much?) as you spin the wheels
- TEST 6: Hook an oscilloscope with "flying leads" to the ABS sensors (notice that the ABS system must be powered)
Hi, It's for a BMW E39 , it's just to give you an Idea how it is to test them, the figures maybe correct or not ? but it's the same principle I believe , Hall sensors ..so milivolts etc. , here's the link :- http://www.bimmerfest.com/forums/showthread.php?t=504679
I'm sure if you look hard enough you'll find some more info. , or use a code reader to isolate the faulty one ?
I'm sure if you look hard enough you'll find some more info. , or use a code reader to isolate the faulty one ?
hi again fixit man
Thank you
I followed the link and read what they had to say ,but wouldn't you think that such a simple operation has been made so complicated
(or maybe on the other hand a simple check is not possible with just a multimeter ???)...
Here's the scenario for anyone else who may follow this thread in the future as believe me I have followed threads and watched vids on
you-tube etc but none on the Z4 specifically and I know that abs systems do differ eg active and passive for instance ..
After using a diagnostic obdii unit to pull the fault code for the 3 yellow warning lights (dsc,abs,brake) on the dash I read that the pump module could be faulty ,however after a little research I find that a duff wheel sensor could also bring this code up and if its a case of testing all the sensors first or shelling out thousands for a new pump module I know what I m going to try first ,now this brings me to my question (before I give in and take it to the stealers for a £100 diagnosis) when I use a multimeter set on resistance (not sure what setting ?) what reading should I be getting from each sensor if it is working ok ?
cheers
Thank you
I followed the link and read what they had to say ,but wouldn't you think that such a simple operation has been made so complicated
(or maybe on the other hand a simple check is not possible with just a multimeter ???)...
Here's the scenario for anyone else who may follow this thread in the future as believe me I have followed threads and watched vids on
you-tube etc but none on the Z4 specifically and I know that abs systems do differ eg active and passive for instance ..
After using a diagnostic obdii unit to pull the fault code for the 3 yellow warning lights (dsc,abs,brake) on the dash I read that the pump module could be faulty ,however after a little research I find that a duff wheel sensor could also bring this code up and if its a case of testing all the sensors first or shelling out thousands for a new pump module I know what I m going to try first ,now this brings me to my question (before I give in and take it to the stealers for a £100 diagnosis) when I use a multimeter set on resistance (not sure what setting ?) what reading should I be getting from each sensor if it is working ok ?
cheers
Ok I thought I would update this thread with my recent finidngs and see if anyone else has any expert knowledge on this subject
I have tested all my ABS sensors and read the following results however I am confused as to the rear readings, can anyone help me further in this diagnosis please ..
using Mmeter set on ohms resistance 100 (continuity) - 200ohms
Front passenger 1.87
Front driver 1.87
Rear passenger 1. (open circuit ?)
Rear driver 1. (open circuit ?)
cheers guys
I have tested all my ABS sensors and read the following results however I am confused as to the rear readings, can anyone help me further in this diagnosis please ..
using Mmeter set on ohms resistance 100 (continuity) - 200ohms
Front passenger 1.87
Front driver 1.87
Rear passenger 1. (open circuit ?)
Rear driver 1. (open circuit ?)
cheers guys
