I need help with my '93 940 Turbo. It has 125,000 miles. The engine just shuts off without warning while driving. It usually starts right up afterward, although sometimes it takes several attempts. This problem has occurred perhaps 10 times since October 2004. The code is always 144, which indicates loss of signal from the ECU. I replaced the ECU with an identical used one, yet the problem still existed. In May, I replaced the Crankshaft Reference Sensor which did not help. Then I replaced the Fuel Pump Relay and the Radio Noise Supressor Relay. The car immediately ran better, however, last week the engine shut down again while driving. I have had two different Volvo mechanics trying to solve this problem, but it is impossible to duplicate. The engine has stopped while coasting, and while accelerating, but never while idling. Any help would be appreciated as I am scared to death to drive this thing.

 

When it shuts off, is it merrily humming along and just dies all at once with no warning? Or does is sputter and cough a few times , try to come back to life, and then croak. Have you noticed anything unusual with the tach when this happens, such as the tach dropping to zero then the motor dying, or the tach swinging up and down, or reading low etc. Anything unusual on the motor temp gauge? Has it done this under differing, or the same type weather conditions, ie always raining or hot? Any other unusual problems with other electrical items, like radio,lights etc? Any stereo upgrades, or other aftermarket electrical equipment?

 

Thanks for the reply. To answer your questions, the car just dies all at once...no sputtering or coughing. The tach drops smartly to zero. Original factory radio/cassette player...no stereo upgrades. The problem has occurred during cool and hot weather. Nothing unusual on the temp gauge. One odd thing, though. When I activate the hazard flashers, the lights on the radio blink off and on with the flashers...don't know if that is significant. Again, appreciate the help.

 

A few things come to mind, but the intermittent stuff is the toughest.
A couple of cheap PM type stuff you can do, if no one has done them yet, is go though and remove, clean and re-seal all engine compartment grounds. Especially the ones on top of the intake manifold ( the ECU, and FI grounds), and the ground at the alternator. Check both cables at the battery for corrosion, if in doubt buy new. Take the cables off of the battery and look closely at the battery post, wiggle them and check for looseness and cracks on top of the case. A bad, cracked battery terminal will stop a motor, and sometimes they are hard to see. If it is over 4 years old, buy a new one. If the spark plug and coil wires have been in service over about 40-50k miles, go ahead and replace them. Replace for sure if they are an aftermarket brand, and replace with OEM Bougicord. Stray voltage from leaky high voltage wires can make ECU's unhappy. Spring for a new distributor cap and rotor also, if it needs them. That is all stuff that should be done anyway.

The ignition power stage module should probably be replaced, and that would be my #1 suspect. Not real sure where it is on the 93 turbo's, but you should be able to find it by following the wires back from the coil.
If that does not do it, then I would guess that it is a wiring problem in the harness to the ECU, and they would all have to be checked.
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Many thanks. I know this is a difficult problem to trace. Your ideas seem logical, and certainly worth trying

 

Pillow, Just came onto the forum to try and solve an identical problem on a 940 turbo with 120k miles on the clock. Identical symptoms including tacho dropping to zero after the engine cuts, but still in gear and rolling. problem first cropped up about a year ago and was diagnosed as a faulty crankshaft imput sensor. This was replaced and the problem went away only to return about 1 year later. Replacing the sensor, coil, HTand plug wires and power control unit (left hand fender near the front) has not soleved the problem which has become progressively worse to the point where it would idle for 5 minutes, cut then not start again for maybe half an hour. I've got hold of a scope to try and trace the problem. There are 3 wires to the sensor coming from the ECU. They are ground, power and signal return. A wire then runs from the ECU to the powercontrol unit and from the power control unit to the coil. I'm only seeing 3volts from the ECU to the impulse position sensor. Does anyone know what this voltage should be?

george

 

You might also want to watch your fuel pressure and make sure the pump isn't overheating and shutting off.
Most of the time when the pump goes bad it will sputter like it is running out of gas but not always.

 

Thanks tech, Clutching at straws I've already replaced the fuel pump relay. I'm using a scope to track down where the crank impulse signal is being lost. I don'ty seem to be getting a signal from the replacement crank sensor, but I'm only measuring 3.0 volts into the sensor. Since the input voltage to the sensor is supplied by the ECU and the input is read by the ECU then I am not suprised that it is not 12v, but I would expect it to be higher than 3.0v. Any idea where I might get this information?

regards,

George

 

The only detailed info that I have is in the 240 Bentley manual for the later LH-2.4 and 3.1 systems. Don't know for sure if the 940 series is the same, but will list what I have in the hopes that it may help. Their test for engine rpm sensor is at the ECU terminal#1 and ground, engine cranking, and should see battery voltage ( 8v minimum). If it was me in your situation, I would do a continuity test on the sensor wire to the ECU. I disconnect the neg battery cable, disconnect the plug at the ECU, then clip my AA battery + to the connector at the sensor, other to ground, and take reading at ECU plug. Low tech, but works. Taking voltage readings sometimes on an active circuit can give false readings, if that circuit is being modified somewhere.If that tests good, then bad ECU or sensor, and yes I have installed bad new parts. If bad, then new wire or connector time.

 

Sorry that I have not logged for a while . Thanks for all the help. Recently, I replaced the Ignition Module (per Ignavus' suggestion)with a brand new one. The problem occurred again...about a week later. The car just shuts down without warning. It usually starts right up afterward, but sometimes takes a few attempts before starting. Always the same code...144. I cleaned most of the grounds. Haven't been able to get to the one attached to the engine block. That is on the list for next week. I checked all the connectors on harness and the ECU. All seem straight. No cracks or corrosion on the battery terminals. Would a poor contact trigger the Check Engine Light? I will pass these suggestions on to my mechanic. He is just as stymied as me. Will update.
Again, many thanks.

 

144 is fuel load code, implying that fuel load is missing or not detected. I would check the fuel pump. On the other thread I didn't have this much info on your issue. Fuel pump would be my final answer.


Matthew