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Low voltage. CEL code 41

Alternator or PCM?

 

Check your voltage on the back of the alternator to rule it out.

 

Could Be crank sensor too, do you have cruise?

 

Didn't check cruise. OD works, tachometer works.

What's "41"?

 

Found it in the book. Flash Code 41 is alternator field fault, open or short.

Happened patching out of the driveway. What's the liklihood it's a wiring problem?

Think I'll reset the CEL and see what happens. Planning on an alternator in the morning.

 

There are two wires, blue and green, involved in a 41 code. They are connected by two small nuts at the back of the alternator. The blue wire contains 12V from the auto shutdown relay when the ignition is on. The other is the connection to the PCM. To test:
1. Turn key on ignition switch
2. Use a voltmeter to measure voltage at the blue wire terminal. If no voltage, then you found the culprit.
3. If voltage in #2 is ok, turn off ignition switch.
4. Connect a 3 foot jumper wire to the green terminal at the back of the alt. Run it neatly away from moving parts. Also connect a volt meter at the battery posts.
5. Now start the engine and go back to the engine bay and short the end of the jumper wire to ground while watching the volt meter. Release the wire from ground after 2 seconds.
6. If the voltage at the battery increased to 16-18 volts, your alternator is ok, otherwise chances are that your field winding / brushes is open/burnt, rectifier bad, stator bad, etc.

 

I went at it with a test light. Bright on one field terminal. Dark on the other field terminal. Bright on the battery terminal.

I think it's safe to say
1. The fuse link is OK (Battery at the big wire)
2. The field is open, Battery on one side, Ground on the other, no output.

Code 41 field open or shorted.

 

Ok, so it looks like you have power to the field1. Did you try grounding field2?

 

No. Don't plan to either.

Hint..... it's already at ground. If the PCM were bad and the field good, it would be at battery voltage.

 

Not necessarily. The field coil is connected via brushes and does not have "true continuity" until the rotor is rotating and one end is truly grounded. Grounding is the function of the regulator.

But if you already found your problem, good for you.

 

The engine was running when I tested it. Otherwise I would have been a real fool to expect output, eh.

I took the alternator off this morning and examined it. The brushes were hanging on the stop, and one slip ring was way worn out. Got a replacement installed, back on the road.