Car has never missed a lick starting or running. Doesn’t miss, runs smooth.

After an evening driving from point-to-point, the car just died while driving about 35mph on clear dry roads. One cough and dead. Cranks fine, no thought of kicking over. Thought it was out of gas, but that was not the case. Towed it home.

No spark condition on each plug, so here is what I did, following the Bentley and Haynes diagnoses for no-spark.

Replaced plugs, wires, cap and rotor on general principles.

Checked main fuse..OK

Checked voltages at coil..OK.

Checked coil..OK.

At the ignition control unit plug, checked the LH load, ground, feed, RPM sensor..all OK.

Checked the voltage at the ignition amplifier in front of the battery. OK.

Now here is the step I don’t understand: Checked the voltage change at the Amplifier plug during cranking. Hooking the multimeter across the No. 5 connection to ground and cranking the engine results in a voltage change of 0.7 to 1.7. The manuals say to look for a voltage between 0-2 during cranking. If the test is positive, then it could be bad, and replace it. What does this mean relative to my results? Has anyone ever performed this diagnosis before?

The next step is to replace the amplifier ($60-80) and/or have the ICU diagnosed, which can’t be done off the car. A local Volvo shop points out that these do not go bad often and I may have missed the diagnoses. Now I am feeling worried.

A new ICU is about $850 discount, $1,100 sucker price. I unfortunately don’t know anyone with a 1990 240 to swap ICUs with.

Any ideas or where I may have gone wrong here?