[BugSplatter]

So I live in California, and my 99 Discovery II failed the smog check because the check engine light DOES NOT come on for the "self check" when starting the engine.
The tech said that the EMS is is sending the signal to illuminate the light but it's not coming on.
I have pulled the instrument panel and there mini LEDs soldered to the board and visually everything looks ok.
Is there a relay, fuse, or other connection that I should look for?
Does the instrument cluster need to be replaced?

Other smog issues.
Code. P1590 abs sensor, but how can you tell which sensor?
Code. P0446 evap system vent control malfunction. Where do I start?

 

[Bosnian Discovery]

Not sure why the SES isn't illuminating - did you take the front of the cluster off to see if the PO maybe taped or painted over the stencil to obscure the lights? It happens more than you think. Your TC/HDC/ABS lights should also be on since you have the 1590 code. If all 4 lights are off you probably had someone tamper with them.

I'm also sorry to say that you have the two most infuriating codes these trucks throw. Neither will affect operation but they have to be off to pass smog.

1590 is a general ABS failure code, not a sensor code.

It could be caused by noisy brakes, bad sensor wires, bad hubs, a shuttle valve failure or a general ABS ecu (SLABS) failure. Most of the time the code is caused by a shuttle valve failure - it's a fairly inexpensive fix described in detail at the top of this forum. You need to get the ABS codes scanned to be sure. Unfortunately, generic OBDII readers won't do it, so you need to go see a dealer or a mechanic who can confirm that his equipment can scan LR brake codes. There are are some handheld scanners available that can do this. I have an Autel AL619 that does great, but it's not cheap at $135.

You will definitely want to avoid getting this code repaired at a shop, especially a shop that's not well versed in LRs. They'll quote for a new ABS pump, new hubs, brakes, rotors, etc. Prices can skyrocket.

P0446 "CVS Valve/Pipe Blocked"

This means that the ECU is detecting a loss of pressure in the EVAP system during the startup test. The loss of pressure could be due to a sticky CVS (cannister vent solenoid), a bad fuel pressure sender, cracks in the fuel pump or vent lines, a bad purge valve, a bad evap pump, etc. Basically the computer is telling you "something is leaking, find it". The diagnostic procedure here is to run a smoke test. It will very quickly tell you where the leak is.

Best of luck. You're probably looking at a cheap fix, but it'll take you a while to find it.

 

[skucera]

It's possible for all the oxygen sensors to age equally, but not enough to push the mixture past the "alarm" boundaries in the air/fuel map. The result might be a failure of a smog test. It's possible, but not likely....

More likely, the catalysts aren't catalyzing the way they should. You can check this with a non-contact pyrometer when the engine is up to operating temperature. Just shine the aiming laser of an infrared pyrometer at each catalyst, and then compare it to the temperature of the exhaust manifold just upstream. The catalytic converter should be 200°-300°F hotter than the exhaust manifold upstream.

Or, you've got lots of little causes each too small to be a problem individually, but added together you're not passing the CARB smog test. The only way to know is to work the problem, investigating each cause and correcting faults as you find them.

Years ago, when I lived in California, you could spend $200 on attempts to rectify a smog test failure, and get a one year waiver. Did they do away with that provision? If so, you've got incentive to pay a Rover specialist to look at your anti-smog system to find the problem, and even if you can't immediately solve it then you can be on the road for a year, with real incentive to get it fixed. Back then, if you failed two years in a row, you had to pull the car off the road. I had a coworker who had that happen. She never got the smog clean enough, so she traded in the car and it was presumably exported to a nearby state with less stringent smog laws, like Oregon.

Good luck,
Scott

 

[Bosnian Discovery]

OP's problem has nothing to do with O2 sensors - neither code is indicative of a fuel metering problem.

Having your SES (check engine) light on is an auto-fail. Not just in California, but in most places with testing. Usually they won't even look at the car if the light is on, but in OP's case the ECU was sending the "ON" command but the bulb was not illuminating - that's why they started the test.