2000 Nissan XTERRA 4WD Computer ? Emissions/Inspection Problem


I will be most grateful for any help on this problem — everyone seems stumped.

My 2000 Nissan XTERRA 4WD with 123,000 miles easily passed inspection for everything except emissions. The inspection shop was not able to get a ready signal from the vehicle?s On-Board Computer System (OBD). For all of the tests the computer ?Not Ready? (OBD Monitor Readiness Status: Catalyst, Evaporative System, Oxygen Sensor, Oxygen Sensor Heater).

The inspection station recommended I drive it for 60+ miles for the computer to reset, and they would try connecting for the emissions test again. This did not work. The inspection station recommended I take it to the Nissan dealer.

The Nissan dealer drove the car for two days, finally diagnosing the car needed a new manifold from the catalytic converter back, and a new computer — this would cost approximately $3,000!

I then took the car to my local mechanic. He drove the car for a day and concluded there is nothing run with the car, the repair recommended by the dealer is unnecessary, and that at some point (0 ? 6 months) the computer will reset on it?s own and the car will pass the emissions test.

In the months prior to this inspection the ABS light has gone on and off randomly. Also the ?check engine? light has gone on, mostly during long drives. The ?check engine? light always seemed to go off after the car had a rest.

Does anyone have any related experiences to share? At the moment I?m looking at:

1. Driving a car with an expired inspection sticker, or?

2. Investing $3,000 I?m told by someone I trust is unnecessary

Stymied and desperate in Ossining, NY

Ask around for a competent emissions repair shop/mechanic. There should be one (competent) in your area. With such a mechanic/shop, the repair will cost much less.

There is a fuse that supplies battery power to the ECM to keep the memory alive. If this circuit is open, the memory of the completed monitor checks will be lost each time the engine is turned off. So make sure the fuse and the circuit is intact.

Also you can get or borrow a code reader/monitor. Get one that allows you to see the monitor status. Drive the Xterra to see if the monitors ever complete. If you find out one is not completing you can zero in on that system to see what the problem is.

Hope that helps. Post back the resolution of this situation for our benefit.

An intermittent drop in voltage from the alternator may be causing the ABS light and the check engine light to flash. And the engine computer to reset, and reset, never being able to complete the MONITORS readiness status…
Have someone to check the voltage output of the alternator. It should be steady.
Check the voltage at the ABS module. If the voltage is erratic, it could be a wiring problem.