V70: Engine code P0302 need help

[cookiemonsterV70]

Hi all,



I'm a new member here.. I've tried to read a lot of posts, but couldn't find the answer for my question.

I bought a 1999 V70 2.4L turbo wagon, and the engine light is on. (distributorless ignition)

Only four cylinders are running. I've changed the spark plugs and the ignition coils (only one was bad). All these things couldn't solve the problem. Spark plugs are good, the compression is good as well. I've took out the E.C.U, and cleaned it, nothing has changed. Does anybody have any idea what the problem could be with my engine? The service code is P0302. Thanks

[big_yin]

P0302 - Cylinder 2 Misfire Detected according to this site

http://www.troublecodes.net/OBD2/Pcodes.shtml

Did you clear the codes after changing the parts?

[cookiemonsterV70]

Originally Posted by big_yin

P0302 - Cylinder 2 Misfire Detected according to this site

http://www.troublecodes.net/OBD2/Pcodes.shtml

Did you clear the codes after changing the parts?

Thanks for the quick reply. I did clear the code, but after couple of minutes the engine light comes up again, and the second cylinder doesn't have any spark.

[deathrider311271]

check the wireing to the cylinder that isnt fireing as it may well have a break in it or been caught at some point so shorting out

[cookiemonsterV70]

Originally Posted by deathrider311271

check the wireing to the cylinder that isnt fireing as it may well have a break in it or been caught at some point so shorting out

Thanks for the suggestions, but I'm already done with all this things and still doesn't work.

[KBB]

I suspect that you have only carried out a visual inspection of the wiring to coil 2 which realy proves nothing. If you want to get to the bottom of this you will need a DVM and a LED test light.

The should be 4 wires in the connector at the coil

Pin 1 Orange/Black is the coil control wire use an LED tester when cranking this will be a pulse signal of 5v to switch the coil transistor power stage.

Pin 2 Yellow is the ignition sensing signal, you will only make any sence of this with a scope meter.

Pin 3 Black this is the ground side of the circuit. I prefer to load this with a H55 bulb (3amp) conected to battery pos, bulb should glow bright if the ground is good.

Pin 4 Red coil supply feed. This should show full available battery voltage with engine running and circuit loaded.

All readings should be taken with the conector connected to the coil and backprobing the wires whilst the circuit is under load.

If all these tests prove positive then suspect the coil is failing under load. Also check the front pins of the connector if some one has been poking test meter probes in the front this can spread the conector pins so they no longer make contact with the coil pins when connected. Also water ingress can corrode the pins creating a sever voltage drop at the connector pins.

If any of the test voltages/signals are missing the the harness will need to be opend up and examined. The are a number of spliced joints in the ignition circuit that can corrode and create a severe voltage drop.

[cookiemonsterV70]

[QUOTE=KBB;1317534]I suspect that you have only carried out a visual inspection of the wiring to coil 2 which realy proves nothing. If you want to get to the bottom of this you will need a DVM and a LED test light.......

I bought it with engine and electric problems. The previous owner has no clue what is wrong with it.
ignition coil plugs 4 pins, 3 wires come in #1 orange/black #2 nothing #3 black #4 red
Thank you

[Thanatos]

As a quick test move the coil from plug 2 to plug 5 and see if the code or problem goes with it

[Chris_Rogers]

The wiring diagrams can be found here:

http://www.matthewsvolvosite.com/volvo-wiring-diagrams

The management system will be ME7 for the turbo engine.

I'd suggest as a start you check there is a 12V supply (red wire) at the coil with the ignition in postion II. If OK then check the continuity of the
earth wire, note there are two so you need to check the correct one for the No. 2 cylinder. Do this with the coil disconnected.
If the above is OK then check the signal wire (shown as orange/black for cylinder 2) back to the ECU, expect continuity readings in the 1 to 2 ohms range.
As you need a special tool to remove the ECU it might be easier to measure the resistance to ground of the 'signal' wires for each cylinder with the ignition off and the coils disconnected, then compare the readings. I'd expect values in the k ohms range.

[KBB]

To be honest I think this is a very simple diagnosis. You have not stated what you have tested and how or what tool you used. Give us a clear account of what you have done and this will help us to help you.

Chris note your reconmendation of continuity testing, personaly When we teach technicians fault finding the use of the ohm meter and resistance is no longer seen as a suitable accurate test. The only way to go is to use voltage drop and load test circuits.

Here is a excillent example as to how ohm resistance testing gives a complete false reading and could have resulted in a new ECU unessesarily being fitted.

http://www.youtube.com/watch?v=44dP6X3QS5A