T4 power loss and erratic idle

[afzalmj]

btw, I remember gettign another error code: Engine coolant remperature (ECT) signal missing...So i bought another ECT sensor (£14.40 or so), but haven't fitted it in yet. Maybe I'll try that someday soon.

The printout I got from Volvo after my software upgrade read:
DSA 221-Engine Load Signal Missing
DIM-11 - ECT signal missing (but my temp guage works fine!)
ECM-13 - MAF Sensor signal too low
ECM-91 - Torque reduction DTC stored in DSA (probably due to MAF, hence going into limp).

[timway]

Hi Afzal, sorry to hear you've still got the same problem, but at least you didn't end up with a megane!

I was also having problems with my DSA, but this was cured by my volvo dealer replacing a relay and part of the wiring loom. They couldn't find any faults relating to the power loss though - I think they hoped that it was related to the DSA problem.

I have a boost gauge on mine, and when it goes into low boost/limp home mode it never goes above 0.5 bar - its strange though because I'd have thought I should get a warning light when it does that. I can get a slightly
erratic idle when it does that too, but not always. Only happens about once every 500-1000 miles on mine, and seems to be fairly random.

I also have a problem with the boost pressure surging/spiking when accelerating hard, but not quite at full throttle - I don't think you get this though?

I'm not sure how you test for a dodgy earth either, I have got a multimeter and digital voltmeter at work though - might be able to do something with those

Tim

I'm sure if the car went into limp mode then the engine light would come on.

First thing re. the earth is to establish the earth point for any suspect components. If all suspect components share the same earth connection then it is even more likely. I can probably work this out which I will try and do at some point soon.

Also it might be problems with the connector into the ECU. Again you need to know the pinout.

Dealers can use an ECU breakout box to monitor the various signals in real-time, something us users don't have although like I said before it would be good if the diagnostics software worked so you could log what the ECU read for a signal in real-time.

For example, as mentioned the coolant temp sensor. If suspect then typically one changes the sensor as this is the most likely area for the fault. If still get fault codes, what can it be? Well either the sensor connector is at fault, the wiring to the ECU / ground is at fault, the ECU connections for the coolant sensor, the ECU ground(s) itself or even the internal electronics! And finally - the new sensor might be duff too! Phew!

Another example with this 'detective' work is some classic VW problem mentioned on VW diagnostics VAG-COM site. A number of seemingly unrelated fault codes come up: fuel pump failure, engine sensors etc. Thing is, they all share the same relay for supply and that is what is actually faulty! So if one has a number of possibly unrelated faults (like Afzal) then you may be able to infer a faulty component like a relay from knowledge of the electrical supply/grounding for said components. Cars are harsh environments for electric stuff, as I said before somewhere the most likely area of a fault is something electro-mechanical such as relays, wiring, connectors, and grounding points to chassis.

Cheers,
Pete

[gnhuk]

Originally Posted by afzalmj

btw, I remember gettign another error code: Engine coolant remperature (ECT) signal missing...So i bought another ECT sensor (£14.40 or so), but haven't fitted it in yet. Maybe I'll try that someday soon.

The printout I got from Volvo after my software upgrade read:
DSA 221-Engine Load Signal Missing
DIM-11 - ECT signal missing (but my temp guage works fine!)
ECM-13 - MAF Sensor signal too low
ECM-91 - Torque reduction DTC stored in DSA (probably due to MAF, hence going into limp).

The following applies to non-turbo engines so should only be reagrded as a guide. The temp gauge uses a different sensor to the ECU - the ECU sensor is under the thermostat and I'm not sure where the gauge sensor is. Haynes implies that one sensor does both tasks hence it is possible to have a fully functional gauge and a duff signal to the ECU........................ The sensor is about £35.

On the T4 engine, according to VADIS, there is a temp sender near the top of the radiator attached to a hose, which suggests to me anyway, that there is probably another somewhere on the block/head.

[afzalmj]

Hmm...some good comments there.

Funnily enough, the 10A fuse for my sidelights kept blowing before the software upgrade -> this seems to be OK now.

What does the Engine Load Signal code mean?

I've had the car remapped today (Upsolute, from stock to 240BHP, 370NM) and the results are fantastic! Who knows, maybe it's cured the problem? I haven't left it to idle and don't want to find out :-P (but will probably do so later, lol)

[foggyjames]

Engine load signal is something of a generic nonsense term in the context of Volvo ECUs (rather like 'broadband' internet!)...but it is sometimes used to describe the 'collected' load data from various sources (MAF against RPM, for example). For example, LH-Jet 2.4 on a 940 has a 'load signal' linking fuel and ignition ECUs.

cheers

James

Originally Posted by gnhuk

On the T4 engine, according to VADIS, there is a temp sender near the top of the radiator attached to a hose, which suggests to me anyway, that there is probably another somewhere on the block/head.

That's the case for early T4s, SFAIK mine (B4204T5 engine) has only the one going into the thermostat housing.

Pete

[gnhuk]

Thanks Pete, I am still finding my way around vadis with a white stick! If there is a sensor in the thermostat housing it probably has a second sensor somewhere on the head for the temp gauge........