1990 Other Nissan Models Spmtr not Wking, Cmptr in Limp Mode

AONE

MEMBER
1990 NISSAN
4 CYL
2WD
AUTOMATIC
51,000 MILES

Do not not drive this car a lot. Recently I noticed the speedometer working erratically. Then it would work and not work. I did not give it much attention. Until the car would not go over about 2500 rmp and gas millage became really bad. I looked into the repair manual and alldata infomation plus Atuo Zone site and determine the car is in limp mode.

I changed the speed sensor and the computer but the these did not help. I tested the battery - the result is good - 12.5V. All fuses are good.

Also, I noticed when I unplug the o2 sensor the check engine light(CEL) would not come on. The same for other sensors I unplug. The CEL would not come on.

When I remove the speed sensor I see the gear in/on the tranmission. It does not look like it is broken off. I tested both speed sensor (old & new) and they give out average.4 v. Right now the speedometer works sometimes.

Any help? Thank you.

1 Reply

AONE

MEMBER
2 POSTS

Last weekend I remove the new speed sensor and put in the old one. Then I changed the speedometer. This fix the speedometer problem.

The car feel much better when driving. Feels more powerful. However, it still does not turn on the check engine light when I unplug any or several sensors.

Now I will figure out why the check engine light does not want to turn on.