VX intermittent shift light and no check engine light

[mxtwo50r]

94 vx. In the last 10k miles replaced distributor, o2 sensor, cleaned egr ports and valve. I can tell the vtec solenoid is still working, as it changes the cam duration about 2800rpms. Sometimes if I downshift and let the car engine brake, the shift light will start working. Once it works if i turn the car off and immediately back on, it doesnt work again. Im stumped. Not sure what makes the shift light function that would be malfunctioning and not cause a check engine light. Gas mileage has dropped alot with this issue. Any suggestions? I didnt do anything to the car right before it stopped working, all the work was done about 6months to a year ago. The shift light will randomly start working after driving the car a while sometimes. Mpg is significantly down with this issue.

[1carnut]

Do you have anything to tell you if it is going into Lean Burn mode or not? I had a 94 VX and was troubleshooting a miss that it had and I know that when I unplugged the O2 sensor that the shift light did not work and obviously no Lean Burn. The shift light itself would not contribute much to a loss of mpg so it seems like it is more likely something keeping it from Lean Burn. Maybe make sure the O2 wiring is good and not touching anything?

[slownugly]

my vx and my vx swapped sedan act weird sometimes. it seems to be temperature related. or maybe drive time? in the winter time my sedan's light would almost never work until i got near home driving through town. in the summer it worked all the time from the moment i pulled out til when i got home. im now driving my vx hatch and it doesnt work until i get home like my sedan does in the winter. it weird :/

either way it doesnt seem to affect mileage or lean burn

[mxtwo50r]

I dont have anything to monitor lean burn. I recently replaced the dist. and I never reset the ecu. I have no check engine light but codes 8 and 9 are stored. Im going to reset the ecu and see if that helps but I don't think it will. Car runs good, no odd issues. Literally just out of the blue decided to start getting crappy mileage and no shift light. I just cant think of what could be malfunctioning that controls the shift light but wouldnt cause a CEL. Map sensor? It used to give me a shift light from the minute I pull out of my driveway. Now even if I get the shift light working, I can turn the car off and start it right back up and no light again. Im stumped. I have found a few threads with similar issues as mine but never a solution. Anyone know what exactly the shift light runs off of? Im assuming the vss, tach signal, map sensor, temp sensor and .....?

[California98Civic]

Originally Posted by mxtwo50r

I just cant think of what could be malfunctioning that controls the shift light but wouldnt cause a CEL.

An open in the wire to the shift light? A dead bulb?

[mxtwo50r]

The check engine light works when the car is turned on before starting it and when I run a ecu code check. The shift light works right before the car is started and also if I redline it in neutral it comes on just before redline. I have eliminated the fact that either light is burned out.

I titled the post that way because 99% of the time when someone says their shift light doesn't work they dont realize that if their check engine light is on the shift light doesn't function. I have no CEL and a random shift light. Also very decreased mpg.

[Frank Lee]

I don't think the shift light problem is causing the fe drop but I will share this: years ago the shift light on my Tempo started behaving erratically; when I got underneath the car to trace the wire from the transaxle I saw that probably the last foot or so of the wire was corroded and the insulation was bad. I soldered in good wire and it's been fine ever since.

[user removed]

Is there any connection to the shift light not working and any component you replaced.
Without a CEL and your mileage has tanked, I would suspect the 02 sensor. Is the 02 sensor OEM or aftermarket. Even the drag of a tire low on air could affect the shift light, but the major loss of mileage without an ignition issue of a CEL points to the sensor (02).

I'm not sure but I would think the ECU would be the source of the shift light signal, based on the input form various sensors, in particular MAP.

regards
Mech

[Jakins]

Hey I just wanted to bring this back because I'm having the exact same problem. Did the op, have any luck? I know a long time ago I got a code for the primary of and it was acting up but it seemed to stop. It still get into lean burn. As of recently it has been doing a misfire code but It turns off by itself every once in a while and my shift light won't work.

[Jakins]

I switched map sensors and it didn't do anything.