QuestionQUESTION: You helped me on a vacuum line question on my 96 Sebring convertible 2.5. I was trying to get them connected before doing diagnostics. I think I have them hooked up right now.
Took it to dealer here in Mexico for computer diagnostic, and waited for them to call me. After 6 days I went back down there and they said, "oh sorry, we couldn't test it as our diagnostic computer won't hook up with a 94 to 97 model. (sense the frustration trying to get something done here.) I took it to mechanic they said had a computer that would hook up to 96 model.
He told me it was "electrical problem, maybe bad computer". I did get close enough to code "1496". Took it to AutoZone and they said it gave "1496" and "P0112". Went to mechanic friend of mine who a diagnostic computer, but didn't use it because his son was the only one who knew how to use it and he was in jail.
He loaned it to me along with the instruction book and I ran the diagnostics and got the following codes:
P 1496-- 5 volt supply output too low
P 0122-- Throttle Pedal Position Sensor A circuit Low Input
P 0123-- Throttle Pedal Position sensor A Circuit High Input
P 0112-- Intake Air Temperature Sensor 1 Circuit Low Input
I had replaced the IAT last week after the AutoZone read out., and I had suspected the TPS due to the severe missing and sometimes dying starting from a stop position. If I moved the pedal more than 1/8 of an inch, it would act like it was going to die, but when I would let up and tap it again, it would finally get me down the road.
Now the question. Is s bad TPS causing the high and low input reading or is the PCM bad and not sending out enough volts (1496 reading) thereby causing the sensors (IAP & TPS) to input bad data.
I would assume I need to check out the PCM first since 1496 (5 volt output too low) was the first readout and according to manual, that is the highest priority. How do I check it?
As I look back over history of problems and how it developed, there is one thing I didn't mention. Last summer I took car to AC shop here which is well respected as the best in town and who I trust. AC would not get cold. I thought maybe expansion valve because sometimes when I started it, it worked fine, other times not cooling at all. But he said it was AC relay. I don't know if he tried replacing it or what but he wound up wiring it direct, by-passing relay. He just made a comment in passing when I picked up the car "that computer is loco". When I started it to leave, it cranked for 5 to 10 seconds before starting, which it had never done before. Always started as soon as you hit the ignition. But hey it was 105 degrees and I now had air-conditioning again, so I didn't worry about it. The missing and bucking on acceleration started a couple of months after that. I don't know if it is related or not. When the weather got cool, I disconnected the direct wiring he had used to by-pass the AC relay
Where do I start?
Duke
ANSWER: Hi Doug,
The IAT code may be 'stale' if you didn't disconnect the battery for a few moments after changing the IAT and before the next time you read out the codes. I would focus on the 5v supply problem. There are three devices that utilitize that supply: the throttle position sensor, the map sensor and the a/c pressure transducer. Begin by disconnecting all three and then measure the voltage on violet/white wire of any of those plugs while you have the ignition in the run position to see what the voltage supply from the pcm is. Hopefully it should be 5v. If not, then you may have a damaged supply circuit in the pcm. If you have 5v then you could try plugging each of them back in, one at a time, and continue to monitor the violet/white wire at either of the remaining plugs to see whether one of the devices drags down the voltage significantly. If so, then that device or its wires would be suspect. The device could be shorting the voltage to ground. I would look closely at the wire harness that supplies each of the devices to observe for melted insulation that could cause a short. This is probably most critical for the TPS because of its location. Also, when you have just the TPS plugged in look at the violet/white wire on another device's open plug, and then keep looking at that wire to see if when you open the throttle the 5v drops noticably (which it shouldn't). I wonder if the a/c mechanic might have shorted the 5v when doing the a/c bypass fix; let us hope not.
On the TPS function you could check the resistance between the center pin and either side pin of its socket as you slowly open and close it. You should find a smooth change in resistance from closed to open with no discontinuities in the resistance reading. The readings will be 'mirror images' depending upon which outside pin you are using in comparison to the middle pin.
Let me know what you learn and we can go from there.
Roland
PS Please 'rate' my answer, and where you see the question about 'volunteer of the month' consider a 'yes' answer if this response proves to be helpful. Thanks
---------- FOLLOW-UP ----------
QUESTION: Preface & to refresh your memory: I live in MX and is not easy to find qualified expert (anyone who knows the answers).
The car is a 96 Sebring Conv. 2.5 motor. Last summer the most highly recognized AC repair shop in my town wired a bypass direct past the AC relay because he couldn't make relay function. Passing comment was "computer is loco". When i started it to leave his shop, it
was slow starting and cranked for several seconds before starting. Before it always started as soon as you hit ignition.
Two or three months later it started missing and stalling on acceleration. Got progressively worse until I was never certain I could get through intersection without dying(literally). If I pressed pedal more than about 1/8 inch, it started missing, if I let up and tapped it and kept repeating this, I could get down the street. Discovered that if I could keep RPM up to approx. 2000 I could get around town. Downshifting, going to neutral and keeping RPM 1500 to 2000 and going into Low when I started, I could get around. I put off
running computer diagnostic because several vacuum lines were disconnected or had been removed (I think when transmission rebuilt), and could find no one here who knew what went where. From internet forums and diagram under the hood, i hooked them all back up (but with
no certainty they are correct), ran diagnostics.
First code 1496 (Low 5 volt output)
Second 122 TPS Sensor A circuit low input
Third 123 TPS Sensor A circuit high input
Fourth 112 Intake Air Temperature Sensor 1 circuit low input
Getting your advice, I was Happy I had narrowed it down, considering I had been told by mechanics here I needed a new PCM, new distributor, new catalytic converter Yesterday I drove it probably 10 miles to buy mutimeter, and kind of like going to the Dr., and the pain goes away when you get there, it ran almost perfect, no missing, stalling, etc. Again this morning, no missing etc. and was on my way to mechanic to run voltmeter tests on those sensors, and as I went over a speed bump,it just died, no missing, no stuttering, just like I turned off the ignition. Dont know if it was relalated to speed bump or just coincidence. Though it had died on me many times in hte past, it was when accelerating and it missed and stuttered and always started right back up with no delay. this time it was a new symptom, it just died and would not start.
Towed it to mechanic and we ran mutimeter tests on TPS, IAT, MAP and AC transducer. they all showed 5 volts. But there was no spark jumping from a plug wires. From what I have read online, crankshaft position sensor, bad PCM, and distributor came to mind. Mechanic thought it crankshaft sensor. When mechanic removed crankshaft position sensor, it no magnetism on the end which mechanic said it should have.
Without having to buy all those parts and doing it by trial and error, how do I test them?
Thanks again for your help. I just want to get this thing in shape good enough to sell. I have had enought
ANSWER: Hi Doug,
I guess you can't try for fault codes?
The crank sensor would be 0320, while the cam sensor in the distributor would be 0340. You can check each sensor by measuring the voltage between the sensor's signal wire and its ground wire while you turn the engine over by hand (because the pulsing is too rapid if you use the starter) with the key in the 'run' position. The two wires in question for each measurement are: crank= black/light blue and gray/black (pins 2 and 3 of the three-pin plug; cam= black/light blue and tan/yellow (pins 1 and 3 of the 6-pin plug). Or you can find these wires at the pcm: black/light blue at 43, gray/black at 32, tan/yellow at 33. You could put pins through the wires to hit the conductor. You should observe a pulsing voltage between 5 and 0.3 as you turn the crank with a wrench on the crank pulley bolt.
The cam sesnor is in the distributor as you probably know and isn't sold separately. I doubt a bump would affect the pcm, and I wouldn't replace that without a code saying so.
I suspect a loose connection of some sort caused the stall but exactly what? I would check that there is 12v on fuse 10 in the power box and 4 and 15 in the box behind the end cap of the dash when you have the key in the 'run' and the 'start' positions just to be sure that the problem isn't in the igntion switch itself. Also check that fuse 8 in the power box isn't blown.
Roland
---------- FOLLOW-UP ----------
QUESTION: Thanks Roland, Before I got to the mechanics shop to try to do the testing you outlined, he had the distributor off and said there is a crack in one of the coils. I did check fuses and relays and O2 10V fuse was only thing bad.
Now, I have found new distributor from Distributor King at EBAy Motors for $193, and with shipping about $250. AutoZone in Eagle Pass TX (closest to me in Mexico) has rebuilt Cordone and with core deposit it is about $250. While we have distributor off, I thought I would replace crankshaft position sensor. AutoZone has a Durolast for about $75. What would you recommend?
AnswerHi Doug,
You could check the pulse signal from the crank sensor to see what it is doing AFTER you put in the replacement distributor so as to avoid any issue with the timing of the distributor (once you take it off it is easier to get another one back in identically if you haven't rotated the engine). Looking at the sensor wires at the PCM plug (43 and 32) would be easy to do as I described. Or you can of course put in the replacement distributor and see if that has fixed things or not, and if not, then check the crank sensor. The history of it dropping out after a bump makes me a bit leary of throwing parts at the problem.
Roland
