EGR and Oxygen Sensor

[NSXPipkin]

Just acquired a 1993 NSX with 42km on the clock. Had a few repairs completed but most bugging is the Check Engine warning light. Tried to decipher problem with the Service Check Connector; however, looks like two sets of problems codes generated. Sequence starts with four long blinks and two short blinks / one long blink and two short blinks. This is then followed by one short blink and then a delay until sequence repeats. Is this possible?

If yes, problem indicates 42-Rear Oxygen Sensor Heater and and 12-EGR respectively. To check on the Oxygen sensor is really difficult; cannot detached the cables and space too cramp. To check on the EGR, need to test vacuum on Hose #5 but no improvement.

Any advise to resolve these issues will be appreciated.

 

[hlweyl]

I believe you can switch out the 2 o2 sensors. Clear the codes and retry.

good luck

 

[Larry Bastanza]

First off, two codes are possible. The rear 02 sensor leads come up over the rear valve cover, and yes it is tight, but you need to look at the service manual on line, it is a simple ohmeter test. I would fix the 02 first then tackle the EGR.

HTH,
LarryB

 

[NSXPipkin]

Thanks Larry, will try to work on the O2 sensors first but if all fails will take on Hlweyl advice. But how do you switch of the two O2 sensors? And will tehre be damage to the engine in the long run if these are off?

And any advice on EGR?

Thanks.

 

[drew]

If the ECU senses bad O2 sensors it will enrichen the fuel mixture.

Rich mixtures will cause "damage", eventually including:
1. carbon build up internally, will lead to pinging (more problems) and burnt valves (as carbon chips off and lodges in the valve seat).
2. lower HP and lower MPG.
3. Ruin your cats and restrict the exhaust (even less HP!)

So get it fixed...you have a while, but it will cause damage "eventually".

 

[NSXPipkin]

Rear O2 sensor indeed faulty and need to replace. Now to source for replacement. Thanks Drew for the advise on replacement.

However, getting no where with EGR - not sure if its Valve or EGR Unit. Any assistance, greatly appreciated.

 

[hlweyl]

Replace the rear o2 sensor then reset the ECU by pulling the clock fuse. After running the car, see if it throws another code for the EGR. I'm not sure if this is the case, but sometimes when one system throws a code, it will frequently trip other codes as well.

good luck

 

[Larry Bastanza]

One thing I forgot to mention. This ECU code indicates a bad heater which is an open curciut for the heater coil inside the 02 sensor, this can also happen if one of the pins in the 02 sensor connector has been pushed back in the plastic body during reassembly, not uncommon. Caref ully check inside the plastic connector housings and make sure ALLL the male pins are sticking out the same length

HTH,
LarryB

 

[NSXPipkin]

The O2 connector is so located midway down enigne compartment with the other end connected to the sensor. Difficult to tell if the pins are pushed in but will test again.

When following Troubleshooting flowchart, the section to check for connectivity between terminal A and terminals C and D individually, there was no continuity between A and C. There was however continuity between A and D. This indicates replacement of sensor on the flowchart.

 

[Larry Bastanza]

Sounds like the heater coil is truly open, time for a new sensor then.

Good Luck,
LarryB