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Help!!! Codes 26,46 and 61.

5K views 24 replies 4 participants last post by  NavyVet 
#1 ·
Hey guys..i have a 1993 Pontiac Firebird Formula LT-1 V8,auto trans 78,500 miles.Been having a good bit of issues with this car,fix one thing then another pops up. I have new alternator,new plugs and wires,new fuel filter.Car is suddenly running really rough when drive and has no power and will bog down when i accelerate.Took it to one shop and they said my optipark distributor is going out,,Today i took it to BF Goodrich shop here and they scanned it and it gave codes 26,46 and 61..(61 being a/c needs more freon(which doesnt make sense and i just had it charged).) Has anyone experienced this problem?? Any suggestions as to what it might be?? I Really need help a my funds are so low,Any help would be greatly appreciated!
 
#4 ·
26 is an evap code, 61 is an a/c code and neither are a big deal.

46 will shut the car off after 1.7 seconds. It is a fuel enable code. When you put the key into the ignition a voltage is sent through the key through the resistor. There are 15 different key resistances. Your tdm (theft deterrent module) is programmed to see the specific resistance that your key puts out. Hopefully you have 2 sets of keys. Try the other set to see if it works. If not, drop the column and make sure the wires aren't chaffed through. There are 2 small white wires that go to the tumbler into the keylock then they plug into and purple and black wire combo. Basically the tdm is seeing something fishy and it isn't telling the pcm to go "fuel enable".

Try shbox.com for useful schematics
 
#5 ·
Thanks, i will try that. i do know a couple of times my car wouldn't start because security light would stay on ,so i leave key on for about 3 minutes and security light will go off and then it will start. Never would have thought it would make engine run so horribly.i do have the other set of keys and will try that as well....Any other help is appreciated very much,,thanks guys!
 
#7 ·
Since it's a speed density engine with no MAF, two main things that can affect performance are the Throttle Position Sensor TPS, and the Manifold Air Pressure sensor, MAP.

The PCM uses throttle position and manifold pressure to determine fuel demand.
You might also change the fuel filter if you haven't already.
 
#8 ·
I tested my map sensor and throttle position sensor voltage earlier.got a reading of 4.98.Thats the right voltage,could they still possibly be bad? I'm usually fairly decent at my car work (have had 3 Camaros, a 70 Chevelle,70 Cutlass,70 Monte Carlo and an 86 Supra along with my current 93 Formula) but this has really got me stumped.
 
#11 ·
Got a reading of 4.98 when and where?
Did the TCP reading increment smoothly all the way from idle to WOT or did it fluctuate?
 
#12 ·
When i tested my MAP sensor i did it wrong,so today i did it again..with key on i get a reading of 4.98 volts.With engine idling i get 1.6 volts,,when i had the motor revved up gradually i get no increase in voltage and i know it should gradually increase to 4.5 - 5 volts..the odd thing about this is one day the car seems to run and respond fine and then next few days it will not run right and hesitates and stumbles...am thinking of going and getting new map sensor but hate to keep buying parts that dont seem to solve the problem.
 
#13 ·
You mean MAP sensor or TPS. the TPS is the one that increases gradually.
Just turn the key to run, the engine does not have to be started.
As for not working and then working, It's called intermittent which is common in electronics, like a volume knob on a radio that skips and stutters.
 
#14 ·
NavyVet,,when i checked the MAP sensor (haynes manual says test for refence voltage with key on for 5 volts) i got 4.98,,then says check it with engine running for 1.5 to 2 volts at idle which i had then while revving the motor(as book says) i get no increase in voltage...as far as the TPS,,its so little space to get to and my voltmeter doesnt have alligator clips and i cant get my probes on the wires(so small),so i was thinking of seeing if aoutozone has a voltmeter with clips to test it..Or should i just go ahead and replace the TPs,autozone has them for 28 bucks...im so confused,,THANK YOU big time for your assistance...I'm trying.lol.
 
#15 · (Edited)
Ah, Ok. I was confusing the MAP and TPS because they have similar readings.
My bad.

If you hit WOT the MAP should hit the max volts momentarily. It measures air pressure as compared to the pre start air poressue. sort of like a baromoeter.
When you first start the engine the PCM records the MAP reading before start and uses that as a reference.
It's how it determines altitude and or barometric pressure changes.

I would replace the MAP sensor and see what happens, you can always replace the TPS later.
 
#18 ·
Did you reset / clear the PCM.
 
#21 ·
Did it make a difference?
 
#22 ·
Navy,,i took it for a short spin today,,not really too far as its super hot again.I seemed to run fine but then again its been an intermittent problem so later it may run like crap again..this evening im gonna take it for another spin and see how she runs.Keep your fingers crossed,im going broke.
 
#23 ·
Ok, got them crossed.:)
 
#24 ·
I took my Formula out for a good spin to see what happens..At 35 i nailed it and got good response,no sputtering.Then on a nice open road,i stopped,put her down into first and nailed it.Ahhh there we go finally,she ran like a bat out of hell! Really good response,power and sound.It's been awhile since she ran like she is meant to,so im hoping that its good to go now.Thanks for you guys help!!! Keep fingers crossed that the MAP sensor was the problem.
 
#25 ·
Great. Sounds like you fixed it.
The voltage reading was a great clue.
Nothing like proper troubleshooting.
 
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