All wheel sensors read 3 MPH, ABS light does not go out. Codes 1-2 & 2-5. Diagnostics says left front sensor or open circuit. Rotating wheel says sensor is working. Calibration between diagnostics & speedometer is off several MPH.

Look at the transmission control module. Sounds like a massive wiring harness problem too.

code 21 is

Open or short circuit in 2?position solenoid circuit for left front wheel

pop possible causes ABS actuator/SFLR or SFLH circuit

Error logs are a great thing. They will help you find intermittent problems and start you off in a general direction of where a problem could be. There is a great level of detail on the justcommodores site on checking error codes logged by the engine management system, but this does not detail anything about the abs system. The abs warning light is not as common as the check engine warning light. Reading through the posts, I haven't found any detail on checking error codes logged by the abs system.

So here it is. For those of you familiar with checking the engine error codes, this procedure is so simple its not funny.

Basically, to check the engine error log, you bridge the 5th (ground) and 6th pins in the ODB connector under the steering wheel.

To check the ABS error log, using the same trusty calibrated paper clip, you simply bridge pins 5 and 12 of the connector.

To find pins 5 and 12, start at the top left hand corner. That is pin one. Going to the right, you count pin 2,3,4 etc. Once you get to the end, jump back to the start of the bottom left level of pins and keep counting. Pin 5 is about halfway along the top row, pin 12 is a little left of the middle in the bottom row.

Reading the error codes is the same procedure (counting the flashes), except now, the ABS light flashes (as opposed to the engine light when checking the engine codes).

The ABS log also uses code 12 firstly, with any errors logged shown after that. If no errors are logged, the 12 will flash again.

Error codes for the ABS error log (VR/VS) are as follows:

12 Diagnostic system operational
21 Right hand front wheel speed sensor fault
23 Right hand front wheel speed sensor continuity fault
25 Left hand front wheel speed sensor fault
27 Left hand front wheel speed sensor continuity fault
28 Wheel speed sensor frequency error
31 Right hand rear wheel speed sensor fault
33 Right hand rear wheel speed sensor continuity fault
35 Left hand rear wheel speed sensor fault
37 Left hand rear wheel speed sensor continuity fault
41 Right hand front inlet solenoid valve circuit fault
42 Right hand front outlet solenoid valve circuit fault
45 Left hand front inlet solenoid valve circuit fault
46 Left hand front outlet solenoid valve circuit fault
55 Rear inlet solenoid valve circuit fault
56 Rear outlet solenoid valve circuit fault
61 Pump motor relay circuit fault
63 Valve relay circuit fault
71 ABS control module internal fault

The above guide has been verified on a VR/VS. Checking the error log on all models prior to VR/VS is the same for the engine log, and I would assume that the same can be said for the ABS log, would be happy if someone could verify this for me.

I think you pulled the code incorrectly, or are reading it wrong. To get code:
1. Jump pins 4 & 9 on OD2 connector.
2. Turn key 2 clicks.
3. ABS light should blink to give you code. (long blinks for first digit, short ones for second. Example: One long blink and three short blinks would be 13).
Honda ABS trouble codes list :
11= Right front wheel sensor (open/short to body ground/short to power)
12= Faulty right front wheel sensor pulse signal
13= Left front wheel sensor (open/short to body ground/short to power)
14= Faulty left front wheel sensor pulse signal
15= Right rear wheel sensor (open/short to body ground/short to power)
16= Faulty right rear wheel sensor pulse signal
17= Left rear wheel sensor (open/short to body ground/short to power)
18= Faulty left rear wheel sensor pulse signal
21= Continous Operation (chipped pulser)
31-38 are all the same: "solenoid"
51= Motor lock
52= Motor stuck off
53= Motor stuck on
54= Main realy stuck off
61= Ignition voltage
81= CPU (central processing unit)

Sounds like the RF speed sensor is bad, normally you can set a multimeter to ohms and put it on the disconnected wheel sensor and see if you get a reading off the sensor. If you do, then the sensor is ok, and may be the ring on the drive shaft.
I would swap the sensor out and reset the codes.

Don't know the vehicle you have ,so if your
front or upstream oxygen sensors are over
100,000 miles, they need changing, on all
your vehicles ,front only, leave rear monitors
until the converters wear out at 12 years or so

Then you can diagnose what ever is left

You got slow & lean sensors
Their old & tired & lost their switching
ability

Google the codes & read up

Change Spark Plugs every 3 years
Clean MAF Sensor-CRC MAF Cleaner
New Air Filter

Hi Timothy:
You will want to have it scanned for any trouble codes to see what area the problem may be in. Just let us know what the code(s) are and we can go from there.

The only thing that I can figure is that it may be that the ABS is activating at low speeds, as there is a bulletin that mentions that with no trouble codes. Wheel speed sensors, dirty.

Bulletin No.: 02-05-25-006B
Date: January 05, 2006
TECHNICAL
Subject: Antilock Brake (ABS) Activation At Low Speeds (Clean Wheel Speed Sensor Mounting Surface)

Models:
1999-2000 Cadillac Escalade
1995-1999 Chevrolet Silverado (Old Style)
1995-2000 Chevrolet Suburban, Tahoe (Old Style)
1995-2003 Chevrolet Astro Van, Blazer, S10
1995-1999 GMC Sierra (Old Style)
1995-2000 GMC Yukon, Yukon XL (Old Style)
1995-2001 GMC Envoy, Jimmy
1995-2003 GMC Safari Van, Sonoma
1995-2001 Oldsmobile Bravada

Supercede: This bulletin is being revised to update the correction and warranty information. Please discard Corporate Bulletin Number 02-05-25-006A (Section 05 - Brakes).

Condition: Some customers may comment on ABS activation at low speeds, usually below 8 km/h (5 mph). Upon investigation, the technician will find no DTCs set.

Cause: The cause of this condition may be an increased air gap between the wheel speed sensor and the hub reluctor ring due to rust and debris built up on the sensor mounting surface.

Correction:
Measure AC voltage and clean wheel speed sensor mounting surfaces.
1. Raise the vehicle on a hoist.
2. Disconnect both the front wheel speed sensor harness connectors.
3. Place a DVM across the terminals of each sensor connector.
4. Rotate the wheel with hand speed and measure the ACmV's. The reading should be at least 350 ACmV's.
5. If the reading is between 200 and 350 ACmV's, remove the wheel, caliper and rotor in order to gain access to the speed sensor.
6. Remove the wheel speed sensor and plug the hole to prevent debris from falling into the hub during service.
7. Clean the wheel speed sensor mounting surface using a wire brush, sand paper, emery cloth, ScotchBrite(TM) or other suitable material. Be sure to thoroughly clean the wheel speed sensor surface. There should be no rust or corrosion.
8. Check the sensor head to determine if it has been warped/distorted due to the corrosion build up or other causes. Check the mounting surface on the sensor head for flatness by placing it on the edge of a metal machinists scale or other suitable straight edge to measure the flatness. Check the sensor for flatness in multiple (minimum 3) positions/directions. If the sensor head is distorted, replace the sensor.
9. Apply (spray) two thin coats of the specified rust penetrating lubricant (corrosion inhibitor) to the complete sensor mounting surface on the bearing hub. Allow to dry for 3-5 minutes between coats. Use ONLY Rust Penetrating Lubricant, P/N 89022217 (Canadian P/N 89022218).
10. When the corrosion inhibitor is dry to the touch (about 10 minutes), apply a thin layer of bearing grease to the hub surface and sensor 0-ring prior to sensor installation. Use ONLY Wheel Bearing Lubricant, P/N 01051344 (Canadian P/N 993037).
11. Install either the original sensor or a new one in the hub and secure the sensor. Ensure that the sensor is seated flush against the hub.
12. Install the rotor, the caliper and the wheel.
13. Place the DVM across the sensor terminals and recheck the voltage while rotating the wheel by hand. The voltage should now read at least 350 ACmV's.

Hope this helps; also keep in mind that your feedback is important and I will appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day.

I have the ABS light on. I pulled the relay to reset it. the light went out but as soon as I start moving the light comes on. I tested the ABS on a sandy road and it does work. I jacked all wheel off the ground. I rotate each wheel and found the ABS light comes on when rotating the rear left wheel. I removed the rotor to examine the the system. I cleaned it with the brake cleaner I still get the ABS light on after rotating the wheel. Is that the sensor that is bad?

The ABS and air bags work together on startup untill the lights go out, this is OK.
If the light stays on then you may want
to get checked out.

need to get abs codes read. it will tell you what wheel to look at.
1.bad wheel bearing, sensor is part of bearing.
2.broken wires to sensor.
3.traction control part of abs