Check Engine Light

Garrick

Member
Good afternoon. I am reaching out to see if any of you have seen the same issue I am having. I have a 1995 NAS D90. Rebuilt the motor with a stage III RPI Engineering 4.6 six years ago. Since then I have added 20K miles and within the last few weeks I have had the check engine light come on and the computer places the engine in “limp” mode. When I look at the OBD reader (under passenger seat) I am not seeing any fault codes.

Thanks, Garrick
 

Uncle Douglas

Well-known member
What Phillip said, no limp mode on your truck. Problem is something basic, air, spark, fuel.
Do you have an aftermarket PROM/chip ?
 

Garrick

Member
Thanks for the reply’s Phil and Doug.

Correct on the limp mode. When it happens the engine reduces the RPMs down to around 1000-1200 and runs super rich until I am able to stop.

I do have the RPI chip upgrade. I have good spark and the fuel pressure is strong. I replaced the MAS and o2 sensors and that seemed to fix the issue for about 75 miles.

i thought the display was broken too. However, when I disconnect the ECU the screen shows the 02 fault code.

Garrick
 

Garrick

Member
Maybe you need new display? 14CUX doesnt have "limp mode".

What are the symptoms?
You sure about that? Sure feels like it when the check engine light comes on and reduces the RPMs to about 1200. I was able to pull over. Reset the ECU and go another 40 miles before it happened again.

Land Rover systems utilise LOS (or "limp-home mode").
When particular faults are identified, the ECM
implements LOS using programmed default values
rather than sensor signals. This allows the vehicle
to be driven to a test and repair site. Once
the fault is cleared, the ECM reverts to
normal operation.
 

Garrick

Member
Quick update... connector For the left O2 sensor and the MAS connector were corroded. Cleaned them and applied dielectric grease. Fault is gone and motor is running great again. Don’t always believe it is the air, spark or fuel. That seems to be the answer so many give and from my experience is not normally the issue.
 

SimonDewing

Well-known member
Which is why you need a decent scan tool so you can look at live data from the various sensors as well as fault codes to diagnose the problem.
 

Garrick

Member
Which is why you need a decent scan tool so you can look at live data from the various sensors as well as fault codes to diagnose the problem.
Agree, my issue was my OBD II reader was telling me the O2 sensors were bad even after I changed them. Ended up being the connections.
 

javelinadave

Administrator
Staff member
Agree, my issue was my OBD II reader was telling me the O2 sensors were bad even after I changed them. Ended up being the connections.
A million dollar code reader would have told you the same thing. It would show a sensor fault for a bad sensor or a sensor that it couldn’t read.
 

jymmiejamz

Founding Member
Callsign: KN4JHI
Don’t always believe it is the air, spark or fuel. That seems to be the answer so many give and from my experience is not normally the issue.
The mass air flow sensor measures air and the O2 sensor measures fuel trim. Those being corroded would have caused a fuel delivery issue, so it was in fact fuel. When someone says to check fuel, air, and spark that includes the things that control them.
 

Garrick

Member
The mass air flow sensor measures air and the O2 sensor measures fuel trim. Those being corroded would have caused a fuel delivery issue, so it was in fact fuel. When someone says to check fuel, air, and spark that includes the things that control them.
😂😂😂😂. Typical.
 
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