I recently swapped out my fuel pump (complete housing) and reset all codes.
a week goes by and this code pops up in heavy traffic, now it wont go away after reset. P1661 (Mil circut) Possibly low voltage? I dont really know where to start besides checking wiring harnesses, but they all look good. What can set this code off? I think a friend of mine had this and he swapped batties and it never came back. Should I try this?

 

From my 1996 factory manual....

http://www.ace1252.com/1996_Z28_Fact...CP1661_001.JPG
http://www.ace1252.com/1996_Z28_Fact...CP1661_002.JPG

 

Cant goto links from work. But the light did not come on driving back to work, no traffic, maybe when heat soaked it only appears.

 

Does the SES light ever come on - e.g. when you first turn the key to "run"?

 

yeah it comes on then goes out now.
earlier while in traffic and car gettin warm fans cycled a few times
the light came on, I had my scan tool in car so I plugged it in and pulled the code, then reset it. A few min later still in traffic the light came back on.
I got home for lunch and reset once again. after car had cooled for a few hours when I was on my way back into work the light never came back(still working ign on) wich makes me wounder because when the pump went out I was in traffic as well and the codes I pulled 1661 was one of them. and after the r2 of the pump and filter I had dissconnected the batt so all the codes where reset.

 

The code is specifically for a problem with the SES light circuit. Has nothing to do with the fuel pump.

Since the voltage is supplied by a fuse (I/P #9) that also services other circuits (BCM, brake switch, instrument cluster, DRL's, aux power wire), it could be a problem on that side, but another device would have to be shorted out to reduce the supply voltage, and that would blow the fuse. And if the voltage supply was so low that it tripped the code, it wouldn't light up the SES light.

Definitely an intermittent condition. The light is either not coming on when it is supposed to, or its coming on when its not supposed to.

I should probably leave the electrical analysis to the electrical engineer... because mechanical engineers should stick to mechanical topics. Feel free to correct anything I said incorrectly

 

I thought you did just fine.

It boils down to this statement.

"Definitely an intermittent condition. The light is either not coming on when it is supposed to, or its coming on when its not supposed to."

Something is wrong with the SES lamp circuit. I would look at the harness between the lamp and the computer along with the circuit that feeds the other side of the lamp(my first link shows you the circuit). Test it as the factory manual directs you. The absolute worst thing it could be is a problem with the lamp driver in the PCM. If the driver is bad, then you will have to get another PCM to fix the issue.

You indicated that the P1661 was one of the "codes" as in multiple codes. What were the others?

 

yes intermittent, light went on today again about the same place in traffic with all the same conditions. 0-5mph stop and go, the temp was right in the middle say 180, head lights on, stereo on. I looked at the batt and it was a little lower then normal when the light came on. as I got some speed 10-20mph the light would go back out. it saved the code like in the FSM. Usually heat soak intermittent would be wires right? Like a bad ground or somthing? If it were a PCM issue would it be like bad transistors(leaking) that are replaceable?

Oh and the other code wa 0122 for the TPS I disconnected during some road side trouble shooting I did when the fuel pump went out.

 

Ok the only time I can duplicate it is when I run the heater full blast with engine at temp in traffic. could the heater be heating up a component in the circut in the dash?

and I did not find any loose or broken wires