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John G.
John G., Honda Technician
Category: Honda
Satisfied Customers: 2652
Experience:  Dealership tech since 1982. ASE and Honda Master Technician.
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1999 Honda Accord EX: a cylinder position sensor code..chassis

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1999 Honda Accord EX with LEV 4 Cylinder engine. The car runs fine for having 140000 miles but recently I have been getting a cylinder position sensor code on the MIL (P1381). I checked the snsor and found it has 894 ohms across both pins and is not shorted to the chassis. I cleaned and reseated the battery terminals and it worked for about a month. Code has returned. Is there any TSB for this issue? Could the yellow wire need replacement?

Hi, I can help.

I'v got some sevice news articles here about that code....


DTC P1381 Set? Check the

Ignition Coil Shield

Troubleshooting a DTC P1381 (CYP sensor

intermittent interruption) in a '98-02 Accord L4 or

'96-00 Civic? If you can't find anything wrong

after following the procedure in the appropriate

S/M, then remove the distributor cap, and make

sure the coil shield is in place and it's correctly

installed as shown. If the coil shield installation

looks OK, then the ignition coil is the probably

faulty and should be replaced.


  • If the ignition coil shield installation is right,

go to step 2.

  • If the ignition coil shield installation isn't

right, properly install the coil shield.

2. Unplug the 4P connector from the alternator

3. Test-drive the vehicle.

  • If DTC P1381 comes back with the

alternator unplugged, replace the distributor


  • If DTC P1381 doesn't come back, go to

step 4.

4. Plug the 4P connector into the alternator, and

use the HDS to do a charging system test. Look

at the alternator diode pattern on the display


  • If the diode pattern doesn't look right,

replace the alternator. A faulty diode can

cause electrical interference that sets this


Customer: replied 7 years ago.

So I'm looking for EMI/RFI interference.


The alternator makes an odd noise when the engine first starts but then goes away. Would this have something to do with it? The sound is a quick "Burt" (low pitch, mechanical noise -not a belt squeal) noise.


How should the coil shield be installed?

What would indicate an improper installation of the coil shield?

Are the alternator diodes available from Honda? Perhaps a rebuild kit> If so, what is the part number?

I personally have never repaired this problem before, but the Honda info is always good.

First the coil. It has a metal shield on the back of it. You must remove the coil to see it.

Take the shield off and make sure there are no tracking marks under the shield or anywhere on the coil. I dont think the shield can be installed wrong, it could be missing.

If an alternator makes any noise its usually got an issue starting. yes.

Honda ha reman. alternators, no parts available. Very good units with 3-36 warranty


Customer: replied 7 years ago.
Is the shield supposed to be plastic or metal in the distributor?

There is a plastic shield, thats not the one they speak of. Its the metal one of the back of the coil.


Customer: replied 7 years ago.

I checked the resistance of the ignition coil primary and secondarys. They both seem within the specs I have. There didn't appear to be any signs of arcing but the Anode tip of the coil had a rounded head that appeared to be drooping on an angle. Is the Anode tip supposed to be straight or rounded? I'm not sure if it is melted.

It shouldnt be on an angle, look in the cap and see if there is a spring in the area where the coil fits. cant remember.

Check your engine number I believe you have the top dist. in this pic.


Customer: replied 7 years ago.
Yes its the top most picture.The cap does have a spring that mates with the coil secondary. Not sure if it is the a1 or a4.

Ok, then the coil is ok.

Look at you charging system then. You can have the alternator tested and see if there is excess doide ripple.

Customer: replied 7 years ago.
Ok, I'm going to pull the alternator and check the diodes. It seems to be strange the way it starts. Are the diodes located on the back side of the alternator?

looks like it


Customer: replied 7 years ago.
Ok I will pull the backup fuse and run it for testing. I'll check the output for proper voltage and do a load test. If it seems out of spec I'll take the alternator in for testing or pull the diodes if necessary. Thanks for your help.

Ok, you're welcome

John G., Honda Technician
Category: Honda
Satisfied Customers: 2652
Experience: Dealership tech since 1982. ASE and Honda Master Technician.
John G. and 5 other Honda Specialists are ready to help you

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