1994 Civic EX Coupe

My ABS sensor light was coming on and staying on when I would drive over 10 MPH or so. The flashing code was 4-4 which my service manual says means right rear sensor. Just to be sure, I did the sensor resistance check for both rear sensors; the left was good (~900 ohms) and right was bad, an open circuit. This was last year.

So this week I'd finally like to get it fixed, and I told my results to my local repair shop. They replaced the right rear sensor. Problem is, the ABS light is still coming on and the flash codes still read 4-4. Local shop didn't seem to know what to do next, so I took the car to the Honda dealer. The dealer is telling me he cleared the failure code, the right rear sensor is good, but the probem is that I need a new modulator, accumulator, and pump for $4281 for parts, labor, and tax.

But the ABS flash code is still saying 4-4/right rear sensor. I retested the right rear sensor myself, and it tests good. Now I'm thinking that the bad ABS components identified by the dealer have atrophied from lack of use during the year I didn't have ABS.

Can the group think of anything else to do before giving up and doing without ABS for the rest of my Civic's life? Maybe finding the parts at a junk dealer?

Thank you!
Vic in Long Island

 

A bad modulator unit is unlikely to throw code 4-4, although a bad control unit (computer) in the rear could.

1) Did you reset the control unit yourself to see whether the code really returns?

2) If so, between the sensor and the rear control unit, test the right rear sensor wires for an open and short.

 

Thanks for your reply.

I did not reset the control unit myself. Both the local shop and the dealer said they reset something, possibly the control unit. I've ordered a code reader that was advertised as being able to reset the error code; it should arrive Monday (July 11 2011), but that's probably not the same as resetting the ECU. I'll look up in the service manual how to do that, or Google.

As for the resistance test, yes, I've done that by disconnecting the orange connector in the trunk behind the right rear seat and testing between the two leads on the wheel side. Before the local repair shop replaced the sensor, there was an open circuit there. Now there is a reading of around 930 ohms, which the manual says is within spec.

 

Looking more carefully at the flowchart in your post, is does say how to clear the malfunction code: disconnect B2 fuse for 3 seconds. (Hmm, maybe Amazon will accept a return on my code reader.) Is that the same as resetting the control unit?

I'll find that flowchart in the manual and go over it thoroughly this weekend.

 

Cancel the order. There's no need for any code reader.

 

Based on what you say here^, you have not yet tested the two wires for a short. If you don't have a short, scout some junk yards for replacement ABS control unit.

 

I followed the flowchart today, and the conclusion from my results is that you are probably correct. For the test of "Check continuity to ground of wire and sensor" I have:

• Each pair except right rear, positive: 2.8K ohms, negative: a fraction of an ohm. This is within spec according to the text at the bottom center of the flowchart.
• Right rear, positive: 5 M Oms, negative: a fraction of an ohm. This is out of spec.

I checked the right rear positive (green/yellow) wire for continuity along its length from the sensor connector to the control unit connector, and the wire has no resistance so it's sound.

So that leads me to the big rectangle in the center of the flowchart indicating control unit. Or as a long shot it could be a faulty connection from the CU to the 18-pin connector. I'll try to find a used control unit and replace. Then I'll get back to the board. Is there any way to know what years, if any, will work other than 1994?

[As an aside: the pin diagram at the upper right is a mirror image of the correct diagram since the view is described as being from the CU terminal side, i.e., the diagnostician's view. It's really from the side where the wires enter the terminal.]

Thanks for all your help!

Vic

 

In the preceding test in the troubleshooting diagram, what resistance did you measure between terminals 14 and 20 of the 18P connector. Was the value within spec?

Based on the one out-of-spec resistance measurement from your "check continuity to ground of wire and sensor" test, a bad control unit is an unlikely source for code 4-4. Instead, I believe the most likely scenario is that the mechanic installed the wrong RR speed sensor or installed it incorrectly. You should check it yourself (see below). Then redo the "check continuity to ground of wire and sensor" test for RR(+) to see whether the resistance measurement is now within spec and whether code 4-4 is cleared.

 

Thanks again. All of the resistances in the 18-pin connector test passed when I did them Saturday. I just now retested the pin 14-20 resistance (making sure the colors matched too: green/yellow to blue/yellow), and it's 930 ohms, close to the center of the pass range.

This weekend I'll pull out the overalls and test the RR sensor install. I'm not understanding yet though how the resistance to ground could be increased by an incorrect install. Will adjusting the air gap affect this?

 

I can't say I fully understand it myself. Inside the sensor, there's a magnet wrapped by a wire coil. Maybe the resistance on the (+) side changes by how far or close the sensor is to the wheel pulser. Another possibility is that the wrong type of sensor was installed. You might test this by moving the left rear sensor to the right rear side and vice versa. If the resistance on the left rear side is now out of spec (follows the sensor), then I think it's safe to assume that the replacement sensor is bad.

 

You might want to pull the sensor and check the end for metal filings as well as the trigger wheel. Sometimes when you go to pull on old ABS sensor they break off in the hole and you have to drill out the part that remains in the hole, if the mechanic didn't clean out the shavings out of the hole they can cause some funky ABS problems.