abs question..

[nc89sho]

with the tester connected, when pulling the abs codes.. should the pump motor cycle? or just stay off?

 

[SHO Type U]

It should stay off, u using an abs code reader? If u have an '89, u dont need to worry about this, '89s dont have abs.

 

[rangerj]

Read the instructions for your tester. Some (most) of the testers or scanners will cycle the ABS in order to determine what is working and what is not. I think it is acually a reaction of the ECU rather that a scanner input.

The more sophisticated scanners will feed signals through the ECU to see if it reacts properly. You may have a scanner that simply accesses the codes, but most ABS units I have worked on will "cycle" when the ECU is scanned. In plain English, the ECU is doing a quick check before it answers the scanners question, that is "what is working and what is not"! The answer comes out in the form of "fault codes".

Just like the drive train electronics the ABS electronics are subject to the same connection and ground problems. So, keep in mind that the fault code DOES NOT necessarily mean that a sensor is bad, or a relay is bad, etc. It means that the ECU is not getting the signal it is programmed to expect under certain conditions.

The "fault" could be caused by a bad ground, a shorted or open wire, and/or a poor connection, say due to corrosion. There are test that can be done to determine if a specific part of the system is faulty, such as the ohms test for an individual wheel speed sensor. The point is, do not react to a fault code by simply replacing the part that the code relates to without doing confirmation tests on the part and its connections and harness.
rangerj

 

[nc89sho]

i'm using a cheap scanner from advance auto, but it doesn't have instructions for ABS. the reason i'm asking is that i'm trouble shooting a code 63 (pump motor speed sensor)

 

[rangerj]

I am guessing but I would bet that your scanner is not intended for accessing the ABS ECU. Your code 63 necessitates a number of test to determine if the pump or pump motor are faulty. Then the pump motor relay is tested, and finally the harnesses between the various ABS components.

I'll post the tests and test procedures for you tomorrow. All you need is a voltmeter and ohm meter (i.e. a multi-meter), and the wiring diagrams posted as a sticky thanks to Bizzy. rangerj

 

[rangerj]

Code 63 re. ABS; If you have trouble determining which pins are which see the wiring diagrams.

Unplug the 4 pin plug from the pump motor and measure the resistance between pin S0 (S zero) and S 1 of the pump motor. S0 is the upper left corner pin, and S1 is the lower right corner pin. The resistance in ohms should be between 20 and 40 ohms. If the resistance is not between 20 and 40 ohms replace the pump and motor. If it is between 20 and 40 ohms go to the next test.

Disconnect the 7 pin connector on the pump motor relay and remove the relay. Set the relay so that the 4 pins are on the left and the 7 pins are on the right. Check for continuity between S0 on the 7 pin side and pin S0 on the 4 pin side. The S0 pin will be in the upper left corner of both the 7 pin side and the 4 pin side. The pins will be virticle rather than horizontal in orientation. If no continuity, replace the relay. If continuity is present - next test.

Check continuity between pin S1 on the 7 pin side, lower left corner, and pin S1 on the 4 pin side, lower right corner (also vertical in orientation). If no continuity - replace the relay. If continuity - next test.

Determine the color of the wire for pin S0 on the 7 pin connector for the pump motor and find this wire in the 55 pin connector at the electronic control unit. Test for continuity of the wire. If no continuity, fix the wire or connection. (circuit 462) See the wiring diagrams.

Do the same as above for the wire at pin S1 on the 7 pin connector and the 55 pin connector. If no continuity fix the wire or any connections between the 55 pin connector and the motor connection. (circuit 461)

An educated guess tells me you either have a (1) bad relay, (2) a siezed pump and/or motor, or (3) a corroded connection. The last in the list of likely problems is a broken or shorted wire.

If you do not have a service manual, and are not familiar with the parts of the system, it would be very helpful to go to the local library and look at the parts of the system and their locations on your model year. Most libraries have service manuals, Chiltons, Motors, Harnes, Mitchels, etc. in their reference section. rangerj