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We have a 2002 Chevy Impala that the ABS, Traction Control and Check Engine lights stay on constantly. We have just replaced both front wheel bearings, (one of them twice), rotors, brakes and new tires all around. We have had a GM dealer look at it and they got the lights to go off, said it was a loose connection. But now their right back on. My husband is a machine mechanic and also does most or all of the work on our cars. He has a high end OBM code reader that also reads ABS. We are getting the codes B1221, B1226, B1232, B1233, and B1245. What could be causing these codes and could you tell me what we need to replace, to be able to clear them and not have them keep coming back on?


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Location: Oregon
does your code reader also give you a description of the codes? All the code definitions I have found for those numbers have nothing to do with ABS or Engine. Does your scanner test for codes by sections? as in engine codes, ABS codes, trans codes, body codes... or does it just jumble them all together? If your scanner does abs codes, what are the abs codes you get? same with Engine codes. what engine codes do you get? Does your scanner also scan pending codes? (or one trip codes not turning on the check engine light yet)

engine/trans codes should be Pxxxx and ABS/traction codes should be Cxxxx. Body codes are usually the Bxxxx codes.

You might want to scan with a Tech2 scanner to verify codes for your vehicle. The "B" codes you're pulling could be audio, window or seat and wiper codes.


   
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All the codes refer to wheel speed sensor. B1221 LF wheel speed sensor input signal 0 - B1226 RF excessive wheel speed sensor variation - B1232 LF wheel sensor circuit open - B1233 RF wheel speed sensor open or shorted - B1245 Low Tire pressure detected


   
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Location: Oregon
ok, i show all those codes as being "C" codes.

ok, does your scanner have the ability to look at the sensors individually? Does it allow you to graph the sensors that in question? If it does you should look at each sensor in question. The tire pressure TPMS code you will have to turn your key on engine off and cycle your parking light on and off three times in 5 seconds then you should hear a click and the tire pressure light should turn off. After the light turns off you go in and clear the history code c1245. your vehicle uses the wheel speed sensors to figure out there is a tire that has low pressure.

the wheel speed sensor codes may not be the actual wheel speed sensors themselves. The wire harness can break inside the insulation where the wheel turns back and forth or where the control arm bounces up and down at. These will usually be intermittent glitches. Turning or wiggling the wire might show the wheels speed signal going away. (easiest to see with the car up in the air and spinning the tire while moving the wire harness)


   
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No our scanner can't look at the sensors indivually, but it can clear the codes and all of the lights in the dash go out, except for the ABS. Then eventually the other lights also come back on. We're going to check out the wiring. Appreciate the help.


   
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Location: Oregon
with the wire harness disconnected to the abs module you could check the signal for the abs sensors for the front wheel speed sensors.

you could check for the sensor at the connector to the ABS module. dark green wire and Tan wire are for the right front sensor, Yellow wire and light blue wire are for the left front sensor. If you unplug the A 1-11 connector you could use a DVOM and check for the signal between those pairs of wires. If you jack up the wheel and spin the wheel you would see the sensor sending a signal. Use AC volts rms. you should see an AC voltage signal as you spin the wheel. Or you could also ohm out the sensor through those wires. resistance should be 850 to 1350 ohms. if you get an ohms reading outside that range you may have a bad sensor. verify by ohming it right at the sensor. If you show an open circuit you may have a broken wire in the harness.


   
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Thanks! He's going to check these with his DVOM. Also got a code P0420, is this the catalytic converter or an oxygen sensor? Car cranks fine, runs fine, gets about 28 mpg. Haven't noticed any issues with performance, just have this code.


   
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P0420 is set when the rear O2 sensor is not showing that the cat is cleaning up the exhaust enough. The front O2 sensor reads how the fuel is being burned and the computer adjusts fuel through the injector pulse. The rear O2 sensor doesn't care about how your engine is running. It only looks at how your cat is burning off the unburned fuel that you engine put out. So your first O2 sensor will be constantly switching above .8v and below .2v. When you cat. is cold (at first start up) the rear O2 wave form will look very much like the front O2. But after the cat warms up it will burn off the extra fuel and the rear O2 sensor should slowly level out (not switch back and forth across the .45V median, usually lean showing that the fuel is burned off)

so you could have a bad rear O2 sensor. but if you could actually graph the sensor in operation, you could see if it is working correctly or not. Most of the time it means that the cat is no longer working like it should.


   
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