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#1
08-09-2013, 01:54 AM
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89 PA code 27
Searched the threads for code 27 but doesn't seem like it's common problem. Lots of issues with cams sensors and this machine is throwing a code 41 too.
 Done one of those before. Code 27 is new territory though. Following the flow chart in the service manual it calls for voltage and test light readings at the transmission cable and connector. I take it that's the 5 wire cable at the front. The drawing lists pins A-E. Anyone have pinout for the connector? Where are these switches inside and what's involved in accessing them? I've worked on a Celebrity 4 cyl that had a bad solenoid. Is this similar? TIA Last edited by Electric_mouse; 08-09-2013 at 01:55 AM. Reason: spelling 
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#2
08-09-2013, 07:03 AM
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Re: 89 PA code 27
Yes, you definitely need a schematic for a 4T60 transmission, showing the harness going in.....
The problem could be the harness to the tranny(broken or shorted wire), or the problem could be inside the tranny(second gear switch or the harness inside the tranny to the switch), or the ECM..... Doing your electrical tests will determine which is at fault.....
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Electric_mouse (08-09-2013)
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#3
08-09-2013, 09:24 AM
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Re: 89 PA code 27
Quote:
Last edited by Electric_mouse; 08-09-2013 at 09:25 AM. Reason: extended message
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#4
08-09-2013, 07:01 PM
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Re: 89 PA code 27
Some large city libraries carry these old manuals.....
Otherwise, just go to a Buick dealership, and have them make copies from an old manual they will have on hand...bring a "Coolata" for the Service Manager....
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#5
08-09-2013, 07:52 PM
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Re: 89 PA code 27
To my knowledge the 4t60 only used pcm commands for the TCC, not the shift points. 91 up was the "e" version that did have shift solenoids. BTW code 27 refers to Quad driver issues, that is what handles high load solenoids or relays in the powertrain, this may not be trans related at all.
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Electric_mouse (08-09-2013)
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#6
08-09-2013, 08:52 PM
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Re: 89 PA code 27
Quote:
 Will check the switches with a test light and meters as laid out in the manual. Will report back.
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#7
08-09-2013, 09:27 PM
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Re: 89 PA code 27
Code 27-
2nd gear switch was closed or grounded when vehicle was in 4th gear, or 2nd or 4th gear switch was open when engine was first started. Code 27 will set if:
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#8
08-09-2013, 09:30 PM
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Re: 89 PA code 27
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#9
08-09-2013, 10:21 PM
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Re: 89 PA code 27
Max , the tranny is shifted hydraulically.....these are switches, not solenoids....
And yes, the ECM quad drivers were sometimes the culprit, but the switches have to be checked out first, and the best place is at the harness connector at the ECM, with the connector disconnected from the ECM, that way you are checking the wiring to the switches and the switches at the same time....If you find a problem, then you continue with the harness connector at the tranny, to determine if it's the harness, the switch or the ECM...
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Electric_mouse (08-09-2013)
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#10
08-09-2013, 10:46 PM
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Re: 89 PA code 27
Quote:
So it's inside we go and that's not happening for a few days. Maybe quite a few days. I was told by a wrecker buddy today that the cover can't be removed without dropping the sub ?? frame assembly, engine and tranny. 
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#11
08-10-2013, 08:18 AM
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Re: 89 PA code 27
Quote:
What's involved here? Anyone have a picture(s) of the inside or links to working on these transmissions? I found a parts picture but I think it's for newer models in early 1990's.
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#12
08-20-2013, 12:56 AM
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Re: 89 PA code 27
Quote:
Pulled the side cover off the tranny. This transmission has been replaced with what seems to be from an Olds. No idea what year or model. It has no second gear sensor. Instead that wire leads to a thermal device. 6K ohms at room temp and climbs when heated. So it's basically useless in this application and car. From all the trans shops I've consulted, this transmission in these older cars use no input from the ECM. The only thing the computer controls is the lock up solenoid. Everything happens hydraulically. One shop said I could probably get away with shorting that second gear wire to ground permanently. Take it for a test drive and see how it performs. One thing I did do was temporarily short the wire to ground. If the second gear switch is open more than ten seconds after starting it will throw a code 27. Shorting it during that period prevents the code. My plan now is do one of two options. Add a timer circuit which keeps that circuit grounded for minimum 10 seconds after starting the engine. Or add a simple relay with a normally closed contact grounding the second gear wire and when the vehicle is placed in drive the relay would pickup removing the ground. Essentially the same condition in which the vehicle is operating presently (sending a second gear condition continually). Because everything seems to be working fine except it's throwing that 27 code because the switch is open during the first 10 seconds.
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#13
08-20-2013, 01:11 AM
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Re: 89 PA code 27
Quote:
It's fairly easy to get access to the guts. Raised the front of the vehicle on blocks. Trolley jack under the sub frame to take the weight. Remove the steering shaft and exhaust. Disconnect the axle, tie rod, lower ball joint and sway bar. There are three large bolts on each side of the sub frame. Remove the inner rear only on the right side. Remove the three bolts on drivers side. Use blocks for safety in case of jack failure and slowly lower the drive side down about 4 inches. Oh, you will also have to remove the three transmission mount bolts at rear and two in front on the drivers side because the cover will not pass the sub frame on the bottom corner. The tranny has to be lifted slightly to make clearance. Not near as frightening as first glance. 
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#14
08-20-2013, 09:49 AM
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Re: 89 PA code 27
Could be wrong here but isn't the 2cnd gear switch only closed when it sees apply pressure, so during a non operational check it would be open normally?
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#15
08-20-2013, 11:55 PM
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Re: 89 PA code 27
Quote:
No the reverse happens. NC contact. Second, third and fourth are all the same (in the original transmission from my research) and all open in sequence as the vehicle changes gears and accelerates. I was told the pressure to operate is low, perhaps 5 lbs. This replaced transmission omitted the second gear switch. It really doesn't serve much purpose anyway, perhaps affecting ignition and fuel injection but not the transmission. The vehicle doesn't operate long in these lower gears so there is very little advantage. Once fourth gear is reached all switches are open. I'm reluctant to have a continually closed or bypassed switch because it may affect ignition and fuel delivery from the ECM. For that reason I will develop a work around as mentioned above. I think someone posted the circuit and description from the shop manual earlier in the thread. [edit] See post #7 by Autojoe. It explains what happens. Second gear 581 org wire must be closed when first started. It must be open in fourth gear operation. (so the possibility of shorting 581 org wire to ground permanently is out). Last edited by Electric_mouse; 08-21-2013 at 03:47 AM. Reason: See post #7 by Autojoe.
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