CTS install

[johnnymossville]

Does anyone know what size pipe thread tap that I'll need to install the CTS in the rear head on my 3400 swap? Someone, I tink that it was "Superdave" mentioned this in a thread but I don't remember when it was. I need to drill and tap the head for the sensor so the dash guage will work. Can anyone help me with this?

[3100 MPFI]

Why not get a 3 wire sensor from a 1996 Grand Prix 3100.

You can then run 1 wire down to it, and it will all work. That is what I did in my 3100 swap into my 1988 Cutlass Supreme.

The 3 wire sensor replaces the 2 wire sensor behind the thermostat housing. The connector for it is the same as the TPS sensor.

[IsaacHayes]

Uhm, 3400 swap just use the 96 CTS 3 wire sender. It goes where the 2wire goes in the LIM where the thermostat is. Then just splice the wires together and use the right pigtail, it's also the same as the TPS pigtail too.

the www.3400swap.com pdf showed the pins and which to solder on where..

EDIT: haha beat me to it. BTW page 14 of the PDF discusses it.

EDIT Again: Or you can put the single wire sensor in a coolant port in the back of the block. Don't ask me where but I've heard of several people doing it.

[3100 MPFI]

I think the 3400 rear port has to do with the older heads. My 3400 heads does not have a provisions for it. My other heads did. My 1996 3100 heads (the stock ones on my pink cars engine) have the port already there, but it has a plug in it. My newer heads (on the 3100 in my gold car), there is no provision for the CTS. It is just smooth there, so I think that has to do with older year 3400 heads.

[IsaacHayes]

Yes older 3100's had it. My front head has a hole and plug for it, the rear has the sensor installed. Did the older 3400's have it too? Maybe.

What really confuses me is a 98 malibu motor I saw has a 2 wire cts, and no other sender?? Does the ECM in that model supply the gauges a signal??

[3100 MPFI]

I decided to look some of this up. My Grandmothers 1999 Grand Am (4 banger, but has the same setup as the 3400), it has a 2 wire sensor only. Let me see if I can figure out how the gauge works in this car.

[IsaacHayes]

I would think that the CAN based cars would work the gauges from the PCM but 99 is still OBDII....

[3100 MPFI]

okay. 2 wires go to the PCM. A - BLK/WHT - sensor ground, and B - YELLOW - ECT sensor signal.

It looks like the cluster just gets it's info from the class2 serial data.

This has got to be the HARDEST to read book I have EVER bought.

Looking at the CLUSTER CONNECTOR for the 1999 Grand Am, there is not even a SPEEDO wire.

This is the pinout for the GRAND AM cluster:

A1 - Lt BLUE/BLK - Turn signal left front
A2 - DK BLUE - Turn signal right front
A3 - not used
A4 - ORANGE - fused battery
A5 - not used
A6 - BLK/WHT - ground
A7 - GRAY - IP lamp feed
A8 - PURPLE - fued output (ACCY, RUN, CRANK type 3 fuse)
A9 - PURPLE - class 2 serial data
A10 - not used
A11 - not used
A12 - not used

B1 - not used
B2 - not used
B3 - not used
B4 - not used
B5 - not used
B6 - BRN/WHT - check engine indicator
B7 - not used
B8 - not used
B9 - not used
B10 - not used
B11 - not used
B12 - SIR indicator output

That is it.

It has to all be controlled through the class 2 serial data with the PCM sending a signal to the BCM, and the BCM translates it.

I know that the Grand Am has the most FUCKED UP wiring setup I have EVER seen, and I have confirmed a lot of it as TRUE.

[IsaacHayes]

LOL interesting. We'll now we know