Hi all. I have a 1988 Bonneville SSE Canadian-spec with the 3800 engine.

My SES light is on almost constantly and I'm getting codes 27 and 64.

According to the Haynes manual, 27 is "Quad Driver Module Circuit" and 64 is "Manifold Absolute Pressure (MAP) sensor voltage low (high vacuum) detected". My car does seem to display some of the symptoms related to code 64 which is lack of responsiveness and higher than usual fuel consumption.

Regarding code 64, the manual advises that I test the MAP sensor. However, I can't find the MAP sensor on my car. Where is my MAP sensor located?

Also, how do I tackle code 27? There is no mention of Quad Drivers in the manual.

Thanks,

Simon

I may be wrong but isnt
27 - gear switch diagnosis (second gear switch)
64- exhaust gas recirculation
http://www.bonnevilleclub.com/forum/...e=article&k=68
I dont think you have a map sensor, I could be wrong.

Well since you don't seem to have an FSM, here are the diagnostics for both the codes you mentioned.

Code 27

Code 64

Hope that helps yah

(FYI, these are from a 90 FSM if it matters, even though it shouldn't.)

Thanks very much guys!

You're right, wjcollier07 I don't have an FSM. I was directly quoting the Haynes manual for the codes. If the FSM says differnet than the Haynes manual must be very inaccurate and is even more useless than I thought it was. Shall I just burn it?

I've never actually found generic service manuals to be very helpful. But its outstanding how much you can pack into one book about one car in one year. Theres nothing like a good FSM. If you ever find one, I suggest you jump on it, no matter the condition.

Its your new fire kindling I don't actually have one myself, thats how useless they are to me.

Hope you resolve your problems soon. And be sure to let me know if I can be of any more FSM assistance.

If my memory is correct, I fixed a similar problem on another car and I think you have to tackle the code 64 first. The car I fixed (a '91) the quad driver circuit is part of the PCM and is only servicealbe by replacing the computer. This however should not be necessary. The quad driver circuit in this case activates an electonic vacuum switch. The PCM is able to detect if the coil in the vacuum switch is open and will result in the code 27. It'* been a while, but I believe when a code 64 is set it can also trigger a code 27. Once the first problem is resolved, it may in turn take care of the second.