Hello folks. My 1995 Trans Sport 3.8 is fine when temps are well above freezing but the more the temp falls, the more likely that the engine will quit when asked to make power as in going up hill or heavy acceleration. If the pedal is pressed too far, the engine fumbles, the tachometer jumps around +or- 1000 rpm or so, the transmission disengages, the check engine light (which is on) flashes then goes out, then the engine quits. Restart is not accomplished until the ignition switch has been turned off then back on. Immediately cranking after stalling will not start the engine. The colder the temp, the worse this gets, meaning the engine will give less power before this happens. When temps drop well below freezing, the engine will not run any longer than about 5 seconds. Fuel pressure is between 40 and 45 psi but never drops below 38 psi , the fuel pump runs when the ignition is switched on, as it should, but does not stop after a few seconds as it does when it is warmer and a timing light confirms that spark is occurring until the engine stops rotating. Sometimes the tach jumps around even when all is fine. In marginal temps when I can drive the van, it will not do any of this when it is good and thoroughly up to operating temperature. Usually this takes about 30 miles to achieve. A new crankshaft position sensor has been installed and made no difference.
Please see this Youtube video of my problem.
Thank you for your help!

Codes:
341 intermittent cam position signal
321 No 18x ignition pulses

Historical codes:
341 intermittent cam position signal
321 No 18x ignition pulses
361 EST line not toggling

I believe you have a failing ICM. Though, when they get hot, they tend to fail that way and not work at all. Yours is failing on the more extreme cold side. A first for me I think.

Anyhoo. I'm reading in my Bonneville 95 service manual which should cover your ICM, and if I'm reading this correctly, it leads me to think its your ICM.


1. I think your constant pump on is because of the ICM itself. Initially, the PCM turns the pump on for 2 seconds to prime the system. Then the ICM tells the PCM to turn the pump on when the ICM sees a crank signal.

2. I think your ICM is staying in module mode instead of going into IC mode. This is why your seeing a 361 code.

Read on...

the wires from the ckp and cmp go to the ICM, i suspect a problem with the wires to the icm, the icm plug or something like that

Will Series 1 still have the same ICM as the 95 Series 2 Bonneville, as in 94-95 all used the same ICM whether Series 1 or 2?

I had to double check, but the part # on Rockauto ACDELCO Part # D1977A goes from 1992-1995 for the Transport

I agree with Mike....does sound like an ICM or connection problem(check females connectors in harness that they are not expanded and are tight).....

Cam sensor problem on this vehicle won't prevent a start, but it can make it run rough.....since you have a scan tool, are you getting a cam signal?

Mike, is 38 psi a little low for this engine?

When was the last time fuel filter was replaced? Whenever it gets cold, and engines have problems in cold weather, I make sure the coolant sensor dat ais ok, and it won't hurt to add dry gas....

I still have my 1994 Olds silhouette 3.8 which got parked due to engine failure. I'd bet I can ****** the ICM from it. Can you give me a hint where I might find it?

It sits below the 3 coil packs.

Which engine do you have anyway?

I'm not sure what the specs are, one source I'm looking at is 48-55psi. But mine is 43 at idle.

But, that is a good point also. If the van is on its original fuel pump, its now 20 years old. Most pumps don't run more than 10-15 years.

Many thanks for the concerted effort! You guys have given me a lot to do and I feel optimistic that the solution is here.

Silly me, I knew where the ICM was but I didn't remember until after I had sent the last post (really, I'm not as think as you must dumb I am). It'* just been a while. The manual pages really have me understanding the operation and interconnection of these components much better. Many thanks. I will hunt this problem down and nail it.

So far I have removed the ICM and checked the connector and three ground wires under the ICM mount plate. Since I do live in northern Michigan it was no surprise to see some corrosion on the brackets and plate but the connections were all clean and shiny. I think the next obvious step is to swap out the ICM with a known to be good one. My Silhouette van definitely has a good one, It ran well and got about 22 mpg before it spun a bearing during a full throttle 90 mph romp. but it is outside at my shop (25 miles away). It'* about 6 degrees outside so I may not get this done today. Please stand by.