Code 54 - Help

[DeanG]

I have been chasing a code 54 (CO-Potentiometer circuit) for quite some time. I finally got all the tools working to get a proper scan. The CEL came on twice less than two miles from home. The car runs well with the CEL lit.

Since this problem started the main catalectic converter, ECU, CO-Potentiometer and Coil pack have been changed. The car also received the 'C' service. It has been to two Lotus shops already. Help I am running out of time and money ($5,000 in repairs and maintenance so far this year). I am already out of ideas.

[DeanG]

Apparently the file is too big to post. I will have to try to get another smaller scan tomorrow.

[GeoffSmith]

Dean,

Did you zip it with WinZip or similar first? You can't post Elan ECU log files directly on the Elan website anyway!

Geoff

[Doug]

Dean, you know you have no CO Pot, right!! You have a federal Elan with an O2 sensor and thus no CO Pot.

Check the diagnosis sheet for that code in the manual -- could the ECU be going bad??

maybe it's a bad ground or loose wire somewhere -- Elans are notorious for little things like that.

-D

[DeanG]

OK here it is.

The ECU has been replaced since the problem started.

[GeoffSmith]

Dean, you know you have no CO Pot, right!! You have a federal Elan with an O2 sensor and thus no CO Pot.

[GeoffSmith]

Dean,

As Doug rightly says, you've got a Fed which is closed loop and has an O² sensor rather than an open loop with a potentiometer to tweek the CO emissions.

Your ElanScan run reports a 9929 PROM in the ECU: this is an open loop Memcal!

It is no the wonder the car is not running well as the O² sensor signal will not be processed and the input to the CO circuit is not there. You either need a closed loop Memcal (or Mountain upgrade) or a CO pot.

Geoff

[GeoffSmith]

I've just noticed you say you've had a new CO pot. Anyway, I've had a closer look at your log and the CO pot signal is bouncing around all over the place as it would with a closed loop system and the O² signal is flat as a pancake as you would expect in an open loop system so I think what I said above is still correct.

Geoff

[DeanG]

It has a CO pot. plugged in quite near the ECU. Is this a bad thing?

[Candles]

Not for the dealer's wallet.

[GeoffSmith]

Dean,

Has it got an O² sensor?

Actually, it might help if you gave some of the history in chronological order - problems, work done, what was replaced, Lotus part number for the ECU if possible etc.

Geoff

[DeanG]

In the hazy past of 2004 we finished a 9,000 mile cross country trip. Approximately 90 miles from home the car started running on 3 cylinders. I replaced the coil pack and everything was OK.

Last year the CEL started coming on occasionally. It was time for some servicing so I made the long trip to DC. I stopped at a restaurant for a bit to eat. When I came out and started the car it was running on something less than 4 cylinders (I would guess only 2 were working). I limped to the Lotus dealer who replaced the coil base plate and the ECU. Driving away the CEL came on in about 4 miles.

When I got home (I hate to admit this) I retrieved the codes and received 54. I a saw a wire dangling near the ECU figured it was for a missing CO pot so I purchased a replacement and put it in. The CEL still comes on occasionally but I have no drivability issues.

After another few hundred miles of driving I started to get a rattle from under the car which sounded like something to do with the exhaust.

I took it to another Lotus shop, this time in NJ to: have a C service, change the brakes pads, adjust the side window fit and etc. The car still had the exhaust rattle and the CEL still came on occasionally.

I brought the car to a respected local exhaust shop and they replaced the cat. When I started the car, it was back to running very rough (2 cylinders???) but the CEL stayed dark. After a couple of start cycles it while sitting in the parking lot it smoothed out and has been running fine for the last few hundred miles however the CEL comes on occasionally, stays lit for a few seconds to a couple of minutes then turns off. Every time I check I find only one code, 54.

The car has 80,000 miles and has been used very occasionally the past couple of years.

[Doug]

Weird Dean!!

I assume you still have an O2 sensor plugged into the car; sounds like you got the wrong ECU replacement -- one for a SE model instead of the Federal/S2 ECU !!

I'm thinking you should remove the CO pot module and if your memcal is for the SE like I think Geoff is pointing out, then what you could do is get a replacemnet piggyback memcal and it will override the improper chip in the ECU

You could either get an upgraded chip from Alan (ESM) or even a replacement regular Federal chip from ESM or Doc Fizzix (if ESM sends him a regular Federal memcal to burn?)

then by putting the proper memcal chip and program into your car it should run at the ECU properly. There's just no way to get a code 54 in a non SE Elan.

[DeanG]

The Original Computer’s (ECM) has 3 Distinct Labels:

---
VEHICLE WARRANTEE INVALID IF REMOVED A082U7223
---
LOTUS ELAN ECM
(49 STS)
(0900083)
---
SERVICE NO. 16132241 *
1.6D MAN FED
14 SEP 1990
16155849 AWKZ
865849S000627808
---

The Replacement Computer’s (ECM)has 2 Distinct Labels:

---
VEHICLE WARRANTEE INVALID IF REMOVED A082U7223
---
SERVICE NO. 16132241 *
1.6S MAN DOM
16 AUG 1990
16149929 AUFH
869929S000245674
---

The difference in markings certainly gives us something to think about.

I have removed the CO pot.

The next thing I will do is put the swap the new and old ECMs and see what happens.

I never throw out Lotus parts. I do however tend to cramp up when working in the heat under the dash. Taking the seat out makes thing better.

[GeoffSmith]

It does look like your closed loop / Fed / States ECU has been replaced with an open loop / Dom{estic} / SE ECU. Check out Alan's website for more information/confirmation. Having looked at the manuals, I can see why you may have been having problems. I presume you connected the CO pot between B12 and A11 on the ECU..... unfortunately, the EGR sensor used in closed loop control version is connected here, so I don't believe you can simply go between open and closed loop ECUs. I've attached copies of tne manuals for clarity.

[ESM]

I would take the memcal out of your old ECU and put it in your new ECU. That should fix it. One possible confusing issue is the condition of the oxygen sensor, which is ignored by the 9929 chip, and may or may not be in good working order.

The 5849 (the last digits of 16155849 quoted above tells me the old ECU has a 5849) is a rare prom id - its interesting to see it in a 49 states ECU. Most 49 states cars have the 1499 (and no EGR sensor). I have seen this id in only one other car, in Norway, and I was able to get a copy of the PROM from it so I do have a copy if necessary.

[DeanG]

It shows the Prom id: 5849 as mentioned above. A short drive didn't give any CEL however it usually takes 20+ miles. I will experiment more after lunch provided I can get an inverter to take the load off the laptop's battery.

[Doug]

good advice from above as always!

I agree that the

1.6S MAN DOM

implies it is for a "Domestic" = UK car, and not an Export.

[GeoffSmith]

It seems strange to me that the part numbers are not different. And what is a Lotus agent doing putting an open loop ECU in a Fed?

[ESM]

The service number indicates the ECU part number - its the same for all turbo Elans (and for all I know the NA too). The second number relates to the memcal and that's the one that varies.