Code 12, check engine light on?

ORTEGA_RIOS

MEMBER
1994 TOYOTA CAMRY
2.2L
4 CYL
2WD
AUTOMATIC
15,000 MILES

The car starts, runs, no hesitation, everything seems operational, but check engine light is solid on (code 12), tried to reset it by disconnecting the battery but as soon I start the car light pops back on solid. I put a new EGR valve, IAC, clean throttle body no change.

1 Reply

BORIS K

MECHANIC
787 POSTS

Hello,

Code 12 - possible causes:

RPM SIGNAL-NO SIGNAL TO ECU FROM DISTRIBUTOR ("Ne" OR "G")
AFTER ENGINE HAS BEEN CRANKED
--DISTRIBUTOR/CIRCUIT
--STARTERSIGNAL CIRCUIT
--IGNITER/IGNITER CIRCUIT
--ECU

As long as the timing belt did not break or jump teeth, code 12 is most likely caused by a faulty pickup inside the distributor. The distributor assembly will likely need to be replaced.

It is possible to check the resistance of the two pickup coils inside the distributor. Disconnect the electrical plug from the distributor. See diagram below.

In order from top to bottom the terminals are NE+ (red wire), NE- (blue), G- (black) and G+ (yellow). G- is grounded to the car's chassis.

Resistance between G+ and G- should be 185-275 ohm cold and 240-325 ohm engine hot.

Resistance between NE+ and NE- should be 370-550 ohm cold and 475-650 ohm hot.

Also check for shorts and continuity between the plug wires and computer.

Remove the distributor cap and check the air gap between the rotors and coils. Should be 0.008-0.016 inch.

How to check wires:
https://www.2carpros.com/articles/how-to-check-wiring

How to use a voltmeter:
https://www.2carpros.com/articles/how-to-use-a-voltmeter

Hope this helps.

Cheers, Boris

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