ECU Failure, Round 2 *Solution Found*

[Flannelman]

Seecond time, 2 weeks.

Went to go home and failed leaving the driveway. Crank it over a couple of times, wont start. Few more times and lights go out except ECU dash light.

Fault codes tomorow, if any.

The only link is by fitting a larger plenum. The first one failed after fitting it too.

Has anyone had this trouble before?

[Dell'Orto]

Must be coincidence, can't see how a plenum change would effect the ECU

[sergei]

What car?
Many cars have sensor ground bolted to inlet manifold, perhaps it is loose/not on?

[iOnic]

You haven't wired something in and used a sensor ground as an earth? Either way I'd pull the ECU case off and have a look for a burnt out trace.

What sort of car/engine is it? Did you diagnose what failed on the last ECU before you installed this one?

[Dell'Orto]

AE101 silvertop

[Flannelman]

Foolishly, no. I didnt check for fault codes in the last ecu.

Its a ae101 levin. 20v with headword and blacktop cam. Its has run fine in the past but the moment this plenum goes on within 500km I get problems. The plenum is just a silvertop one thats been extended 40mm to the firewall.

I will get some fault codes and go from there.

Sorry for not posting what car/engine. Was at meremere on friday night so was very tired.

[sergei]

Are you sure it is not blown caps issue? Opening the ECU will show...

[Flannelman]

No fault codes found, continuous flash.

sergei, will try this tomorow. Dam bad luck for me if it is.

[Flannelman]

Sooo, after a fiddle I gave up...

Untill this last week. ECU was taken to an electronic shop who tested the caps. They were fine and the circuit board passed the eyeball inspection too.

Installed today and found same issue. Engine started on first go, wouldnt accept throttle and eventually rpm fell away till it stalled within a minute.

After some brainstorming with a friend over ECU issues in general I continued on removing the plugs to sensors and testing for fault codes until removing both VVT and Engine Coolant Sensor. THIS combo has resulted in the engine now starting, running and accepting throttle.

Replacing the plug to either VVT or the Engine Coolant Sensor and the engine returns to its no run situation.

My guess is that the Engine Coolant Sensor is faulty and needs replacing but Im checking if anyone else has seen this and has another solution.

[rollaholic]

someone will be able to give you specs for CTS presumably.

[iOnic]

Pull it and test resistance vs temperature. Pulled this calibration out of my Corolla map. All Toyota CLT sensors of that era are pretty much the same. You may even be able to swap the gauge and ecu sensors and retest.

-20 15k
20 2.5k
60 550

[Lloyd]

Since we have ECS, CLT and CTS, lets include ECT and THW too.

And as above, general specs are 3000 ohm cold and 300 hot, makes it easy to remember.

[Flannelman]

SORTED Engine Temperature Sensor. The center one that goes to the computer. Replaced and now all is good

[allencr]

SORTED Engine Temperature Sensor. The center one that goes to the computer. Replaced and now all is good

Thanks.
Never put out a code/s?

[Flannelman]

No, no fault codes untill the unit was disconnected. I have not tested the sensor for lack of a multimeter but I suspect it was sending a temperature that was over 90C when the engine was cold. This trimmed the injectors to suit this. On a dead cold engine, there was not enough fuel enrichment to accept throttle.

As a side note, the harmonic pulley, keyway and cam sprocket have been severely damaged from a loose pulley bolt. The keyway has chewed out a large gap in the harmonic pulley and made a smaller yet similar gap in the cam sprocket. This resulted in a change in cam/ignition timing of two teeth retarded. This didnt help my cause in finding a cure, but more that at 297,000km this engine has had a hard life and will soon need to be retired.

[Lloyd]

The coolant temp sensors often don't go out of range, they just give a reading that is within spec, but not even close to reality. Live data will probably show something like -7 degrees and fuel to suit no matter what the engine temp.