Does P0700 prohibit a catalyst efficiency test?

Discussion in 'Chevy Truck Forum' started by NitroJunkie, Jan 22, 2018.

  1. NitroJunkie

    NitroJunkie Member

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    Howdy boys and girls. I have a 96 Tahoe and I just put a fresh rebuild on the 4l60e. She's driving perfectly at the moment. A few months back I had swapped out the starter when it started popping off of the flexplate. Simple fix, but I disconnected the battery cable to do it.

    I left it sit for months, and then took it in for a DEQ test (just a computer scan) and it failed because the catalyst monitor was not ready. Yeah, I just forgot I had wiped the computer and I figured I'd take it back once everything reset. Never had a problem with it resetting the catalyst monitor before. I drove it for 2 weeks, not ready. 2 more weeks, still not ready. That's a 20-minute round trip including highway driving at 55 every day. Now I'm smarter and have been checking readiness with my el-cheapo code reader. Still won't reset. Took it on a 45 minute cruise up to the mountains over the weekend, still not reset.

    The only thing I've noticed is that it has P0700 set (does not light the light). Definitely not a shift solenoid or the lockup solenoid as it shifts and engages lockup perfectly. The tranny is now modified to eliminate PWM for TCC lockup (using the transgo style fix turning the TCC signal valve into a spring-regulator for TCC pressure). The TCC will now lock up anytime the TCC solenoid is energized, regardless of apply percentage. I don't think that would throw P0700 though... Many, many people use this fix for worn out bores on the TCC signal valve. The torque converter was a stock-stall reman, but it does seem to have about a 200 RPMs higher stall than the old one did. I would think that would throw the slip code P1870 if anything. I don't have access to a scanner that can talk to the TCM at the moment. I actually worry that the tranny is shifting too quickly for the computer's shift-adjust range thanks a shift kit, hence P0700. In that case I'd need someone to disable the shift adjusts, which costs about as much as I put into the rebuild.

    Anyway, the immediate question, obviously, is would P0700 prohibit the catalyst efficiency test? All the others monitors are ready despite P0700. Also, this thing has a crazy low thermostat too, if it has one at all... Temp gauge has marks for 100, X, 210, Y, and 260 (not a linear gauge). She runs halfway between 100 and X right now. Is there an operating temperature criteria for the catalyst test, and maybe I just don't reach it in the dead of winter? If not, anyone know the specific drive cycle I should follow for a 96 tahoe with a 5.7 to get this thing to reset?
     
  2. Kennyray

    Kennyray Moderator
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    The drive cycles you did should have reset already. I think you need to replace the tstat.
     
  3. leolkfrm

    leolkfrm Full Member

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    should be a 195 t-stat, change it clear the code and do a drive cycle
     
  4. NitroJunkie

    NitroJunkie Member

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    For anyone else who is searching on this, the issue was the coolant temp sensor. The gauge and the ECM get their information from different sensors. The computer's sensor apparently starts to read colder and colder temps as it fails. I replaced the $15 sensor and have a whole different truck now. I only realized the issue when the truck started to idle high because of the sensor, but lots of other symptoms have vanished. It used to hold third for a mile or so on a kind of cold day, but no longer. When you look at the temp gauge, there is a bold line between 100 and 210... The truck had to get to the last thin line before that bold line before it would engage TC lockup. Now it engages when the needle touches the first thin line after 100, which takes about 1/3 or 1/4 the amount of driving.
     

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