ECU Self Diagnostics Mode 4? 89 240sx Bouncy Speedometer - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

i-Slide · 03-28-2013, 10:35 AM

Hey guys.

I searched/read several dozen threads all over the web about the analog speedo issue and I never really saw a very good mention of using the ECU lights to find the problem so I am curious.

So I just bought my first car for pretty cheap and it's an S13. It's a little rough and has some problems but runs ok. No mods or anything and KA24E 5 speed. Zilvia has already been a great resource for reading.

The speedo is bouncing. Sometimes it 'works' but it reads 140kph when I am at 3000 rpm in 5th (should be 100kph? haven't crunched those numbers yet). If I am parked and turn on the interior lights the speedo responds and the needle kicks up for a second, so I'm thinking loose stuff in the cluster or something to do with the cluster/wiring/grounds. I also see some mention of checking some fuses. But that's besides the point.

I wanna know about the ECU diagnostic. Mode 3 threw the 'all good' code 55. The real time mode 5 didn't throw anything when I tried it. Mode 1 and 2 looked like they worked as well.

Mode 4 looks like it worked. I didn't have gps speed on a phone or anything, nor do I remember the RPMs, but it seemed to turn on at ~20kph like it is supposed to. So it went like this.

Parked: No lights
Approaching 20: Red light comes on
Hit 20: Red stays on, green comes on
Over 20: Green stays on

And then vice versa for slowing down. This surprised me because I don't think the FSM mentions the red light doing anything ever for the test, but whatever. It had this repeatable pattern.

What does this tell me? The sensor is working, as is the connection to the ECU? Everything from sensor to ECU is OK?

Am I wrong to say that doing this test (using RPM to verify the 20kph) really narrows it down to two things:

-problem in the path between the ECU and speedo
-problem at speedo/cluster

It seems like a nice way to narrow down a problem.

I have other questions about Mode 2 but I'll spare those for now. Primary concern is trying to get a safety test so this is problem #1.

Forgive me if this is somewhere in another thread. I DID search.

i-Slide · 03-28-2013, 07:11 PM

Nobody? TLDR?

long story short, anyone ever use Mode 4 for the speedo? What exactly does it rule out?

03-28-2013, 10:35 AM	#1
i-Slide Join Date: Mar 2013 Location: Ontario Age: 34 Posts: 2 Trader Rating: (0) Feedback Score: 0 reviews	ECU Self Diagnostics Mode 4? 89 240sx Bouncy Speedometer Hey guys. I searched/read several dozen threads all over the web about the analog speedo issue and I never really saw a very good mention of using the ECU lights to find the problem so I am curious. So I just bought my first car for pretty cheap and it's an S13. It's a little rough and has some problems but runs ok. No mods or anything and KA24E 5 speed. Zilvia has already been a great resource for reading. The speedo is bouncing. Sometimes it 'works' but it reads 140kph when I am at 3000 rpm in 5th (should be 100kph? haven't crunched those numbers yet). If I am parked and turn on the interior lights the speedo responds and the needle kicks up for a second, so I'm thinking loose stuff in the cluster or something to do with the cluster/wiring/grounds. I also see some mention of checking some fuses. But that's besides the point. I wanna know about the ECU diagnostic. Mode 3 threw the 'all good' code 55. The real time mode 5 didn't throw anything when I tried it. Mode 1 and 2 looked like they worked as well. Mode 4 looks like it worked. I didn't have gps speed on a phone or anything, nor do I remember the RPMs, but it seemed to turn on at ~20kph like it is supposed to. So it went like this. Parked: No lights Approaching 20: Red light comes on Hit 20: Red stays on, green comes on Over 20: Green stays on And then vice versa for slowing down. This surprised me because I don't think the FSM mentions the red light doing anything ever for the test, but whatever. It had this repeatable pattern. What does this tell me? The sensor is working, as is the connection to the ECU? Everything from sensor to ECU is OK? Am I wrong to say that doing this test (using RPM to verify the 20kph) really narrows it down to two things: -problem in the path between the ECU and speedo -problem at speedo/cluster It seems like a nice way to narrow down a problem. I have other questions about Mode 2 but I'll spare those for now. Primary concern is trying to get a safety test so this is problem #1. Forgive me if this is somewhere in another thread. I DID search.

03-28-2013, 07:11 PM	#2
i-Slide Join Date: Mar 2013 Location: Ontario Age: 34 Posts: 2 Trader Rating: (0) Feedback Score: 0 reviews	Nobody? TLDR? long story short, anyone ever use Mode 4 for the speedo? What exactly does it rule out?