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When you are in Drive and accelerating, at about 40 mph you should notice a slight "shift" when
the torque converter locks to prevent slippage (saving fuel) and the rpm should drop slightly. If that is happening, then the system is o.k., assuming that when you subsequently step on the gas the converter unlocks, and then relocks when you lift off the gas and are still going over 40. If not, then the electrical signal to operate the solenoid comes from pin 55 of the 60-way plug of the smec (probably by grounding one end of the solenoid) on the black wire, as well as 12 volts coming to the plug-in on the dark blue which derives from the J2 connection at the alternator. So do check to see that the solenoid has continuity, and that you are getting 12v on the dark blue lead, and that the black lead has continuity to pin 55. If all that checks out and you aren't getting lock-up, then the mechanical operation of the solenoid could likely be checked out with the transmission still in the car, because it is mounted on the valve body transfer plate.

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Recently I ran into a very perplexing problem on what would normally be a very simple, straightforward system to diagnose and test. One of our subscribers called about a Dodge van that stalled when coming up to a stop sign.

He had checked all of the basics, including EGR. He even had the idle speed turned up to 1000 RPM and it would still do the same thing. I asked him to unplug the torque converter lockup solenoid. Sure enough, the problem went away. The next step was to check the inputs to the ESA computer to see why it was keeping the solenoid energized. The speed sensor, idle switch and coolant temperature sensors all tested good, so I had the tech go to the Part Throttle Unlock (PTU) relay and check the voltage on all of the wires when the problem occurred to see what the computer was doing to the relay to control it.

He called me back even more confused than before! He gave me the voltage readings from all of the wires. The wire that the computer would normally put a ground on did so until vehicle speed went below 45 mph and then it went to 12 volts. I said it sounded like normal operation. He said, "Yes, except the output wire to the solenoid also still has 12 volts on it, keeping the solenoid energized." Simple enough. The relay was sticking, causing the problem. Replace the relay and the problem should be solved.

He called me back two days later to tell me he had ordered and installed the new relay and the vehicle still had the same problem. I once again suggested that he get readings on all of the wires on the relay -- but use a voltmeter this time. I had discovered previously he had been giving me voltage readings from a test light! Easy mistake to make -- bright test light, 12 volts ... right? Not in this case (when the vehicle acted up). He did see the control wire go to 12 volts, but the other side of the pulling coil was at 18 volts. When I suggested that he check the charging system, he found that yes, indeed, it was overcharging. I asked him to replace the Electronic Voltage Regulator and the charging system operated normally. He test drove the vehicle and the stalling problem was gone.

What had happened was that the voltage drop across the pulling coil in the relay was enough to keep the relay energized even when the computer released the ground on the control wire.

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Janek123: Mul endal ka üks 318 tbi '88 pukkidel seismas sai teisega päris mitmeid aastaid sõidetud..aga nüüd asjast oli ka umbes samasugune probleem aga veel lisaks ei tahtnud alati käima minna- "uurisin puurisin" ning lõpuks avastasin et jagaja kaane alla oli ta elektrooniline katkesti ning sinna läks 3-ne juhe millest üks oli korpusesse sisenemise kohapealt katki, mitte küll väliselt aga selleni lõpuks jõudsin . niisiis isegi saate aru kui katkestist signaali vahetevahel ei tulnud siis suri mootor lihtsalt välja .Tööle läks aga iseenesest- ennem kui asja tuumani jõudsin ajas ikka hinge täis küll.

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