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Car wont pass smog, help

im posting on my boyfriends behalf, he’s got an 88 nissan 300zx, we are trying to get it to pass smog, and it failed because the check engine light wont fault/come on. it doesn’t work i guess, and its not the bulb, we’ve got the dash ripped apart, everything looks like its factory wrapped as far as the wiring harness, its a digital dash, we are stuck as to what it might be for the check engine light not working??? can someone please help !!!

The problem might be with the computer itself.

When the ignition switch is turned on, the Check Engine light should come on. This is the self-test of the computer.

If you’ve found there’s not a problem with the bulb or the circuit then you have to start thinking there’s a problem with the computer.


I too would suspect the ECU.

I should point out too that your BF really should recognize that he may be in over his head on this one and head for a shop. He may even need a dealer for this one. I doubt if he has the expertise, equipment, or access to the documentation to definitively diagnose this one.

Or he could just replace the ECU and see what happens.

Good gravy, that’s a 27-y.o. vehicle! What [expletive deleted] state requires that sort of nonsense on a car from the Reagan administration?

If it’s the one I think it is, might be “civil disobedience time”: rent a mailbox in Carson City, apply for a plate and be done with it!

I cannot agree with committing a criminal act to get around a civil issue.

Here in California, even older vehicles than that need to be smogged

^That’s why I deliberately mentioned Therauox’s (SP?) “civil disobedience” idea: when a state abuses its authority by passing overreaching laws that produce no tangible benefit, and are unduly burdensome to the poor…not only should one not feel a moral imperative to follow said law…one should feel morally obligated to break it!

That’s what failing 30-ish y.o. cars for bad self-diagnostics is: given the small number of cars involved, it produces no real environmental benefit. By the aged nature of the cars involved, it disproportionally impacts the poor…and in CA’s case, likely disproportionally impacts one particular ethnic group. It basically is a way of the state flaunting its power, like most bullies, simply because it can.<p

I’m not necessarily telling OP to do this, just opining that this is an unjust law–and should she choose to do so, she (and BF) should not feel one tiny bit bad about it. Such open resistance to unjust laws tends to lessen the likelihood of similar unjust laws being passed–or at least enforced once passed.

Remember: nobody said the car didn’t pass the sniffer–this is a “bad self-diagnostic” issue only, at least presented as such! BF could assuage whatever eco-guilt he feels over the microscopially small envirnomental consequences of his actions by “sentencing himself to community service” and picking up trash in a park one day a year.

Go, OP, and “stick it to the man”: just don’t get caught!!! :wink:

Meanjoe, I agree with you (and HDT) in principle, but the OP should understand that falsifying one’s residence to avoid smog testing is very likely a criminal offense. It is in my state. Civil disobedience should only be done by someone who understands the risk and is willing to accept the potential consequences.

Ripping the dash apart seems like an extreme measure just to sort out why a CEL won’t illuminate.

Has the boyfriend been playing around with the ECU, or computer? I vaguely (very vaguely) remember something about a screw in the side of the ECU which involved several test modes and possibly the ability to turn the CEL off during a certain test procedure.

@meanjoe75fan‌ If California catches you monkeying with vehicle registration information, it’s fairly serious. A guy I know got charged with a felony because he tried to trick the state out of getting his car licensed there. I agree with you in principle that smog laws on 27 year old vehicles are absurd, but when you’re encouraging people to engage in acts of civil disobedience, I find it ethical to find out what penalties they’re facing and warn them of such.

Yeah, you’re right. I was being at least a little “tongue in cheek” about what OP ought to do re: registration.

(I was NOT being anything other than literal when I called out the state of CA. Shame!)

I would hope that OP wouldn’t go ahead and take action like this without due diligence and deliberation…and as stated, such action could indeed have serious legal repercussions. I stand behind what I said about it being 100% morally acceptable, though.

California over-reaching its authority? Say it ain’t so Joe. They’re only getting started. I think they would like nothing more than having a 27 year old vehicle off the road.

^And, now that they have the precedent of forcing OTR diesels to retrofit to modern standards, there’s no reason they couldn’t apply the exact same legal principles to an '88 300Z…or a '64.5 Mustang.

I remember raising a stink about this, here, and getting an underwhelming response from folks who don’t drive professionally. (“They came for the OTR truckers, and I said nothing, because I was not an OTR trucker…”)

When I was in high school, I had a 1966 Vista Cruiser. It was originally a CA car and IIRC it had an air injection pump on it.

Really cool 300zx web site. It’s factory service manual. First link shows the check eng light.

Say whatever you want about California, but remember there are almost 35,000,000 of us here and the wind blows from West to East. Every bit of junk that gets blown into the air by a car, 1 year old or 27 years old, flows East over the rest of you.

Double-check that the bulb works and is connected to the ECM. Some smog places aren’t so careful, and don’t check that the CEL comes on with the key in “on” but engine not started, instead they only check that the CEL is off with the engine idling. So owners would have an incentive to disconnect the bulb somehow, maybe removing a pin in a connector, etc. Perhaps that has happened. So make every effort that the bulb really does work, and it is properly connected, and that the circuit which feeds the bulb is being provided 12 volts. Also check that the ground for the circuit is connected to the chassis, as to turn on the bulb the ECM will often grounds one side of the bulb, the other side always being connected to 12 volts. If the ground (usually the ECM ground) isn’t making a good connection to the chassis, that will prevent the CEL light from coming on. That would usually cause other problems too, but it is worth considering anyway. You definitely want to avoid replacing the ECM or monkeying around w/the dash unless absolutely necessary. Unless you have a certain amount of electronics skills and tools, it might pay you to have a pro do the diagnostic, tell you what’s wrong, then you & BF fix it yourself. Best of luck.

I’m assuming OP and the boyfriend are not driving the '88 300ZX because they’re poor

I’m assuming they’re driving it because it was a cool car. Perhaps we’ve got some nostalgia going on here

Poor people would be driving an early '90s Nissan Sentra, for example, not an older sporty car

Move to Florida, no smog no safety inspections since 1989…if it runs you drive it. Smog inspections just nothing but BS. We stick out in the ocean so no worry about the smog coming in from other states which make you have your vehicle inspected…I have an 89 Mustang GT and bought new and never had an inspection done. EPA can kiss it.

I have an '88 Supra. After a small stumble when I got it 8 years ago, it passed emissions until it was grandfathered under GA rules at 25 years old. Now, I’m emissions exempt and living large!