here is an easy one for you guys out there... the coolant temp sensor... I have a 305 tbi LO3.. now i know there are 2 sensors for the temp on each side of the block.. on the drivers side we have the temp sensor which gives the reading to the internal consor.. then on the passenger side we have the fan switch which reads the temp and sends it to the fan and turns the fan on. NOw my questions is... first of all is my info correct so far?

NOw there is another sensor that i'm not sure what it is... It lies right in front of the TBI at the tip of the manifold. Now When i diplay my codes i'm getting code 15... my question is, which sensor is this refering to? i know that the one on the front of the manifold works because when i disconnect it while the car is running the car DIES down in idle. code 15 says that it is a faulty cts. let me know what you guys think.. new sensor? which one? do i even know what i'm talking about! thanx
Bill K

 

bill,

your info is mostly right. i dont know what sensor you mean on the drivers side of the block. the only thing i know of on that side is the O2 sensor and that on the driver's side header. the CTS (Coolant Temp. Sensor) is the one on top of the engine near the thermostat in front of the TBI. The CFS (Coolant Fan Switch - sometimes called the Radiator Fan Switch) is on the underside of the car on the passenger side. the CFS is a huge pain in the a$$ to get at.

Code 15 is for the CTS with a low temp reading. As far as I know there isn't a code for the CFS as it is just a switch and doesnt 'report' any data to the ECM. so i would say go to your local parts store and ask them for the CTS and replace it, there only a few bucks. Shouldnt take you more than 5min with a crescent wrench.

hope this helps

 

ok cooll i will do just that...

the switch on the drivers side is on the block just like the coolant fan switch just of teh drivers side.. when i disconect it.. the gauge inside my dash switches off and doesnt read the temp.

Thanx for the help i'll kepp you updated

 

i am still not sure what it is you are disconnecting on the drivers side. unfortunately i am at work and my helm's manual is at home. i will check on it tonight when i get home

 

You are absolutely correct on the driver side and pass side temp gauge. On the Intake is the ECM's Coolant temp sensor and that is apparently what is throwing your code. And no, they aren't that expensive. Good luck

 

Unbelieveable.. for the first time in my cars life( with me as owner) it is running perfect! not 1 trouble code! idle is high cuz i messed with it a while ago but other than that not one code ! thanx to all you guys but thanx to vaders tip I practically have a new car
Thanx to all
Bill

 

The one in the driver's side head, between the #1 and #3 spark plugs, is the sending unit for the gauge. That's all it does is work the gauge.

The one in the water outlet, where the upper radiator hose goes, is the one that tells the ECM the engine temp; commonly referred to as the Coolant Temp Sensor or CTS.

Code 15 usually means that the ECM thinks that the engine temp hasn't reached a resasonable level (120° or something) within 10 minutes of running. This can be caused by the CTS being disconnected, or defective. If it's hooked up, and you're getting the Check Engine light with a code 15, just replace it.

 

TBI,

Now, go back to the TPS adjuistment and minimum air position adjustment of the throttle body.

Start the engine and allow it to warm up. Shut off the engine. Disconnect the EST bypass connector. Turn on the ignition but do not start the engine. Place a jumper wire between the 'A' and 'B' terminals of the ALDL connector under the dash.



Wait about 20 seconds for the IAC to extend fully, then unplug the IAC electrical connector.

IMPORTANT: Remove the ALDL jumper before proceeding!

Start the engine. Set the throttle stop screw to obtain the desired idle RPM using a hand held tachometer instead of the unreliable dash gauge. Set the RPM to 500-550 RPM. Shut off the engine, then reconnect the IAC and EXT bypass connectors. Start the engine and check the TPS voltage between the 'A' and 'B'terminals of the TPS connector. 'A' is ground, 'B' is positive. If the voltage is not between 0.47-0.61 VDC, loosen the TPS mounting screws slightly and rotate the sensor to get the voltage as close to 0.54 VDC as possible. Snug the screws, disconnect the meter probes, and close up shop.

Then you'll have an almost-like-new car.

 

again thanx.
well i dont have the rpm or voltage meter but i know how to set the idle to get it colse then i'll check it with the guage.. i think my friend has one... anyway I set the idle now and from the dash gauge it read about 700 P/N and about 550 600 in drive and i'm extatic car runs great and when i shift manually(being an auto matic) first gear has never been quicker.
tomorrow i'll try to get a voltage meter and rpm thingy and make sure everything is set. i went to 2 auto parts stores and they both didnt have either i was upset but they werent auto zone or pep boys any way thanx for the help. finally i can concentrate on springs and paint and rims
BIll

 

well now i got 2 of the codes instead of the 3 now i still get 32 (EGR) and 42 (EST distributer) so i'm not out of the woods yet but the car still runs great. tomorrow i'll buy a new egr and thencheck all the wires leading to the dist and see what works.
I just dont get why i get code 42 cuz usually that indicates the car wouldnt start ? i'm baffledmaybe i was ment to always have trouble codes... i'll have to use black tape like homer simpson haha

 

code 15 is back again. well ta least the car runs great.. today i'm still going to buyan egr valve but idk what to do anout the coolant temp circut or the est problem ohy well maybe one day i'll win the lottery and buy a ws6 2002 trans am ( my dream)

 

Did the MIL lamp turn on again, or did you just scan for error codes? The codes you generated a coupledays ago are likely still being listed unless you cleared them. The ECM will retain error codes for the last 50 engine run cycles, so you may be reading old codes. You can clear them by disconnecting the battery or ECM fuse for about five minutes. This will also clear the BLM tables, so the car may run a bit differently until new data tables are written based on your current sensor inputs.

 

I always clear codes after i think i've fixed something i usually disconnect the batter cable and take out the ecm fuse. I ran the car for a whole day and didnt get a code when i check that night but the next day i got them all ack again.
ALso i dont know what a MIL lamp is. I have a key i stick into the acdl and read the codes the car flashed thats all

Thanx for the help
Bill

 

TBI,

O.K., just checking. Apparently, your ECM still doesn't like what it is reading in the CTS circuit. One thing you can dois to meter the resistance of the CTS at a know (or presumed) temperature and compare it to the specification:



If the sensor's resistance is reasonablyclose,you may have a connection problem between the CTS and the ECM.

BTW - As long as we're throwing around acronyms, "MIL" = Malfunction Indicator Lamp, or the "SES" lamp on older cars. The newer term for OBD-II PCMs is "MIL",but it's the same thing, really.

I'm guessing that since the CTS was a suspect, you've already looked at the connector when you replaced the sensor. You might want to drop the ECM out of its bracket and check/reseat the edge connectors there just for arguments' sake.

It's also possible that the 5VDC reference voltage from the ECM is not correct, from either a connection or AC interference from a failing alternator, or a poor engine ground or ECM ground connection. Got that DMM handy yet?

 

yeah i got my new voltage meter.. now that you mention it, i did the head gaskets on this car..( why i got it for 500) and maybe when i was plugging the wires back to gether i didnt ground something right. since it was my first head gasket job and i was flyin blind and had no help whatsoever.. i think i did an ok job
today after work i'll tae a look at the ecm and it bracket and i'm gunna check the wire leading to my distributer.. i read that i might have a bad modual. "hei" modual
Bill

 

heres a quick question... do you still think the cts is makeing the rest of my problems? cuz i'm gunna change the egr valve anyway.
i think i've always had an egr problem too since i got that code when i first got the car running.
so replace or wait till cts is ok

 

also.. with timing.. when the est wire is disconnected do you set the timing on my car tyo the book degree which is 6 or TDC or 0*?
I set it to 6 with the wire disconnected. but it runs great where it is with an idle at 700

 

TBI,

The '15' should be repaired first, since it is such a critical sensor to engine operation.

Now you'll get to put that new meter to work. Check the CTS resistance. Also, when the connector is removed, check the resistance of the black wire in the connector to a good engine ground. There should be zero ohms, or no more than the resistance of your meter leads. If you have resistance, you need to check the ECM and engine ground connections. If you have a good ground connection, before you reconnect the sensor, turn on the ignition (do not start the engine) and meter the voltage across the yellow and black leads of the connector. You should get 5.0 VDC. If that is O.K., turn off the ignition and reconnect the CTS.

The '42' could be cause by a failing HEI amplifier/switch module - or not. Your '42' could also be caused by setting the base timing with the EST bypass connector disconnected. Reconnect the connector after the iming adjustment and clear the codes.

The base timing is your call. Every engine is different, and if you plan on running better fuels,the 6° BTC setting could be right for your case. It certainly isn't too much for a stock car running 91 or better octane.

You should check the connections to the HEI module in the base of the distributor. Remove the cap and rotor and visually inspect the connectors. Make sure the mounting/grounding screws for the module are clean and tight. Since they also supply a ground for the module, you might want to remove, clean, and reinstall them if they show signs of corrosion.

When you are in the distributor checking the HEI module connections, carefully disconnect the two-wire connector from the pickup coil and read the resistance across the coil. You should see between 500-1,500 ohms for a good pickup coil. 850 ohms is about perfect. Also, check each of the leads to a good engine ground. You should have no continuity, or infinite resistance. If there is a resistance reading, you may have a failing pickup coil. Remember that you can read the resistance of your body, so try not to touch the meter probes when checking the coil/ground resistance.

I'd wait on the EGR valve until the '15' is resolved, but if you want to play with the meter a little more, disconnect the EGR solenoid connector and meter the resistance of the coil. If it is open (infinite resistance) you have a problem. Also, check the ground connection to a good engine ground. Again, you should have zero ohms.

 

ok i had work but b4 work i did a quick engine inspection. i found 2 great revalations... first my cts connector was bad.. i found this out cuz when i would push down on the wire the rmp would jump up and when i would let it alone they would bog back down. so i cut and spliced and put the new connector on and it seems to work. right now i'm, gunna clear the codes again and see if this did the trick.
i have a question new now... i have a miscallanious vacum line hangin and melted..

ok the two hoses that run into the fire wall into the heter core go into this little plastic thingy with 3 inputs. at the very tope of this plastic thing is a tiny port for a vacume line... the problem is that the other end has no end. but i cant seem to find where it connects to.
if you dont understand what plastic thing i am talking about.. it hangs right around the oassenger side head at the front and is in no way attached to the engine. it just looks like a gateway for collant.
let me know if you can figure out where the line goes to.
i'm, off to clearthe codes again.

 

What you are describing sounds like the hot water control valve for the heater core. There is supposed to be a vacuum line connecting it to the HVAC control head inside the vehicle. If you have no vacuum line but are still getting heat, someone probably bypassed the valve.

 

sound about right but the main thing is that i cleaered the codes and after a full days worth of driving, i dont get tcode 15 anymore and as well as code 42. The only thing left if the egr. still get code 32 but i dont have to guess anymore

I did find out where the vacume line goes to. it goes into the fire wall as well. I actually bypassed the heter core to get it to stop overheating. but i dont get heat and havent in a while but i'll fix the heter soon enough. my main priority is my codes.
I actually have a pisture of the unit i couldnt figure out but having many problems getting onto my comp and on the internet
anyway thanx for the help

 

Check the EGR solenoid resistance. It should be around 100-150 ohms. If that is O.K., check the vacuum lines to the solenoid and EGR valve itself. If the lines are intact, start the engine and allow it to idle. Reach under the valve cap and raise the valve diaphragm with your fingers. The engine should stumble and probably die. If so, the EGR valve ports are not plugged and the intake passages are clear.

If something is revealed in one of those test, repair the problems and check again for error codes after driving.

Beyond that, diagnosing the valve operation is a function of the MAP sensor. The ECM expects to see an increase in MAP signal when the EGR is commanded open by the ECM. Simulating the operation of the EGR on the car is diffcult, since it is probably a positive backpressure type (TBI engine), so beyond those tests, a new EGR valve may be your only recourse.

On a somewhat related note, I had a TBI engine that stored a '32', wouldn't idle at the correct RPM, and was hard starting. After much hair-pulling, I discovered that the freshly-replaced PCV valve was the wrong flow for the engine, and it caused constant high MAP readings, excess idle air, and the '32' since the MAP couldn't detect the EGR opening. Installing the correct AC PCV valve solved the problem, and I'll never use another Fram PCV again if I can avoid it. I'm not saying that is your problem, but any vacuum leak can contribute the the '32'.

 

well i'll do the tests and see what happens.
if any vacume leak could cause "32" then that could be it. I found most of my vacume lines melted through and i hyad to replace the ones i saw. the most recent one broke on me and i cant reach where it goesbut idk
I'll test teh egr and connections and probably change the egr valve itself and i'll get back to you if anything changes
again many thanx
BIll

 

ok well the part i was talking about is in the picture.. currently the vacum it leading to nowhere... also i got code 42 back again but only after i started the car and something sounded off.... it was actually like if the car was running normally and you unplugged the est wire as it was running.. well thats how it started and the light came on right away.
i'm also getting a backfire in the tbi on take off.

otherthan that nothing has changed cts works fine and tomorrow i'm buyin new egr, open element, and breather.

 

sorr the pics so big dont know how to make smaller

 

Did your new EGR valve solve anything?

 

i dont know yet because i was changing my shifter cable and one of the bracket bolts that holds he cable to the trans is stripped so i need to get a new one but i'll let you know hwow everything works

 

heres an update... my new shifter cable is in but it doesnt put trans all the way in park which is annoying but its beter than nothing so i put the center consol all back togther.
My new egr seems to be working good so far.. although i still havent erased the codes again... the ses light sometimes doesnt come on at all and i would be driving for more than an hour.. SOmetimes it will come on about 15 minutes after driving... i'll erase the codes again with my new egr and see what happens.
i also put the open element on and i love the suicking sound it makes.. almost sounds like a blow up valve. too bad my exaust drowns it out haha
i was reading about how your susposed to buy a non drop aircleaner but i didnt see any with a drop. i'm not sure if mine even is non drop. i was also reading about that you have to buy a bolt kit or something because the stock one is too short.. mine was all bolt right up and replace. did i buy the right thing? it looks great and seems to be working fine.
also i havent been backfiring anymore.. after i changed air cleaners it seemed to be backfireing more. But now it hasnt backfired yet all day.. i'm praying the new egr fixed that but idk i'll have to wait and see
All in all I hope i dont have to fix anything for a while i just want to enjoy my bird and cruise around town for a while