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Q: Service Engine Soon Light - Code P1870 on 1996 Chevrolet Lumina

Two weeks ago I had a complete tune-up to the tune of $457.00. The Service Engine Soon ("SES") light was on at the time when I brought it in for the tune-up. I was told at the time that the light might come back on but I should bring it back and they would reset it.
So, today I brought it back as the SES light is back on. I was now told that the code that comes up is P1870 and that it has nothing to do with the tune-up but that it's a transmission problem.
What does P1870 mean with regard to my car? And what is the estimated cost of whatever fix it needs.
This is upsetting to me because I thought if the light came back on it simply had something to do with the tune-up which is how it was phrased in a way -- you know, "If it comes back on, just bring it back and we'll reset it." It made me think it had to do with the tune-up. Now, I'm told it's a transmission problem. I've dealt with this guy before and never had a problem, so now I don't know what to think.
Another question. Should I bring it to the Chevy repair people instead here in town? Do you think that would be better?
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the problem is not with the guy, it is with your car. hundreds of things can go wrong at anytime. the car is 15 years old. he resolved your problem when you went there. the problem would have happened even if you would not have got your tune up. dont blame him for your cars problem. let him check it out and tell you what the problem is this time.
I assume your car is running fine??

Thank you for that totally unhelpful reply. I am not blaming him for the light being on, but I am blaming him for leading me to believe that it had something to do with the tune-up. The car is running fine and I appreciate that, but the light is still on.
was the code present when you first presented the car for repair?? if it was, then shame on him for not investigating the issue.

Hi, Roy
I don't know what code was there when I brought in the car since I personally don't know what you need to check out these things.
But since the Service Engine Soon light was on at that time and I specifically told him that it was on, he said he'd check it out.
After the tune-up was done, the car was fine for about a week; the light was not on; and then suddenly it was back on.
The day I picked up my car after the tune-up was finished, he said that if the light comes back on to stop back and they'd reset it. I mean, what would you think? Wouldn't you think that the light had to be reset from the tune-up work? At that time he did not say anything about it being related to a transmission problem. That's why I'm very concerned.
I've decided to bring it to the Chevy dealership here in town and let them look at it. I just feel I need another opinion at this point. I love my car and it's been a real good car for me and plus it's paid for. Important, especially in today's time. LOL
Also, I need the air conditioner to be fixed and the guy who did the tune-up never would give me an estimate. When I called the Chevy dealership, they gave ma a definite quote based on the facts of what's been happening to the AC and what's been done so far.
What issues are yo having with the air conditioning? If it is not working at all there may be several thing going on. In most cases technician want repair a part of the system and guarantee the work. They will repair the entire system with replacement remanufactured or new to support the warranty they issue.
Some customers may comment on a harsh 1-2 upshift and the Check Engine Light or Service Engine Soon indicator is illuminated.
Typically, these vehicles will have been driven more than 32,000 km (20,000 mi) before this condition occurs.
The scan tool may show a DTC P1870 set as a history code.
A harsh 1-2 shift or DTC P1870, caused by wear in the control valve body, may be difficult to duplicate when the transmission temperature is below 93°C (200°F).
The condition may be due to wear in the control valve body. This wear occurs in the bore that contains the TCC isolator and regulator valves, and results in poor, or no, TCC apply.

DTC P1870 is a type B code. The conditions for setting the P1870 DTC must occur on TWO CONSECUTIVE TRIPS (ignition cycles, with a drive cycle) before setting a P1870 history code.
When the conditions for setting DTC P1870 are met (first trip), the PCM commands maximum line pressure and harsh 1-2 shifts are the result.
This may result in a harsh 1-2 shift with no history code if the conditions for setting the DTC required for the second trip are not met, on two consecutive trips (Ignition cycles, with a drive cycle).

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