’96 Pontiac Grand AM and code P1870 [Archive] - GrandAmGT.com Forum


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06-21-2005, 08:22 PM
I have a ’96 Pontiac Grand AM and the Check Engine/MIL light keeps on popping up in the dashboard. While servicing the car for other problems at the GM dealership, they told me the code is P1870 and it means that the transmission has an internal slipping. But they also said this code sometimes pops up by mistake and during the road test they couldn’t definitively say something is wrong with the transmission. The transmission fluid isn’t dark and doesn’t smell like burnt.

Now, the car was heavily used by the previous owner, it has close to 130K miles on board… I use it only once in a while, as a second car, and I keep resetting the computer every time the check engine light shows up. But the light keeps on showing if I drive it long enough… Sometimes I do feel a drop in power (or traction) but I can’t really tell it’s the transmission (the car is automatic).

Has anyone else had this specific problem with this, or a similar Pontiac model?
How could it be fixed? And is there anything that I can do to further troubleshoot this problem?

Thanks much!

06-22-2005, 12:44 AM
Does your transmission actually slip? I.E. Does your engine RPM climb without you going anywhere in gear?

At that mileage its highly possible that your clutches are toast and its time for a rebuild. Couldn't tell you without driving the car though.

06-22-2005, 06:36 AM
Yeah, I've had this problem for a while. I still haven't had a chance to get it fixed yet, but so far everything else seems to work ok. It's probably the clutches (like mentioned above).

I know this isn't much help, except for the fact that you're not the only one with this problem

06-22-2005, 10:12 AM
I had the same problem, and it was a bearing in my tranny. Got it fixed and rebuilt, cost around a grand. As long as your not leaking fluid, you shouldnt have to worry about bearings. Just watch the left side under the tranny when you pull out of places in reverse...if you see a trail then your in trouble, it would be the same problem i had.

06-22-2005, 11:53 AM
Thank you all for your quick replys.
As far as I can tell it doesn’t leak fluid but I’ll keep an eye on it. As for RPM spikes, yes, it does happen but only when I start the car in the morning and put it into gear, for a couple of seconds, and then becomes stable. It seems to act up more in cold weather, so I attributed this behavior to a moody oxygen sensor, but I could be wrong.

Anyway, while driving, sometimes it does look like the car is not responsive enough when I rev up the engine, but it’s not an obvious problem yet, at least to me. But I guess something must be wrong with the clutch, because the light unavoidably pops up sooner or latter.
Any idea how much should I expect to pay for a clutch job, if I decide to have it fixed (automatic)?

06-22-2005, 04:19 PM
my in-laws blazer gave that code as well. No noticeable driving issues but only thing that fixed it was valve body replacement. ECM compares input speed (rpms) to output speed (vss) after the vehicle is warmed up and is driving with the converter locked up it compares the 2 and if it varies too much from what it should be it sets the code, could be anything at 130k really - valve body, lockup solenoid, worn clutches/bands, etc. etc. Good luck with it!

06-23-2005, 12:19 AM
Expect to shell out at least $1,500 for a rebuild on the low-end.

09-12-2005, 03:45 PM
my check engine light is back on after replace the gas cap which we thought was the problem. no leaks/ everything works get/ no smells nothing indicating any problems. end of dash fuses okay. cars works great. 1998 ga se 3.1 auto

09-18-2005, 09:08 PM
found problem was holes in gas pipe from gas tank.

09-18-2005, 09:17 PM
With DTC P1870, if it is "currently" set (the MIL (Check Engine) will be on; however if the DTC is indeed current, it does say that the torque converter clutch will be inhibited and also 4th gear will be inhibited. This meaning you won't have 4th and your torque converter won't lock up and therefore you will be running at higher revs than normal. From the above posts, it seems the problem must not be that bad for the car; however, you will likely suffer from poorer fuel economy as a result of no 4th and no TCC.