Hello all. I was wondering if anyone knew much of the Throttle Postion sensor. I was getting all sorts of codes on my '93 caravan with the 3.3l, with about 154000 miles. #21, 24, 25 and 32 and the check engine light. I replaced the TPS and all of the original codes disappeared. However the check engine light and code 24 have not. The parts guy said it may take a few days for the computer to recognize the new part or has he put it, to reset. Is there any truth to this or was he just blowing smoke? Thanks in advance.
Rick99
09-10-2008, 09:58 AM
I wish we had a trouble code list for 93 Caravans, so I could look those up. Do you have the code definitions handy?
I'm used to OBDII stuff, but the engine management principles are basically the same. In answer to your question-- the computer may adjust some of its adaptive settings to a new part like a TPS (since the full open and full closed resistance may be slightly different between sensors), however, this should not result in a code setting. If you disconnected the battery for a while it should have reset the computer. Any codes that come up after the reset are for problems that still exist. It may be that the other codes haven't come up yet because their tests haven't run, but they will come up again later.
Anyway, if you, or someone else, can post up the code definitions, we can give more help.
damndragons
09-10-2008, 08:57 PM
Thanks, for shortness sake I will list the codes that have came up previous.
Code 21= oxygen sensor high or low readings
Code 24= TPS high or low readings
Code 25= AIS high or low reading
Code 32= EGR sytem failure
Rick99
09-11-2008, 08:16 AM
These code definitions seem to match up with the definitions we have for 96-97, except for 25:
<LI>Code 25-Idle Air Control (IAC) motor circuits-short or open detected in 1 or more of the IAC control circuits.
I think the acronym changed at some point-- "AIS" standing for Automatic Idle Speed motor.
It's important to see an accurate and full code definition so here is the stuff we have for 96-97, which I think is the same for your vehicle (if someone knows better, let me know):
<LI>Code 21-Oxygen sensor signal-neither rich or lean condition is detected from the oxygen sensor input.
<LI>Code 24-Throttle Position Sensor voltage does not agree with the MAP sensor.
<LI>Code 24-TPS voltage above or below the acceptable voltage limits.
<LI>Code 25-Idle Air Control (IAC) motor circuits-short or open detected in 1 or more of the IAC control circuits.
<LI>Code 25-Target idle not reached-actual idle speed does not equal the target idle speed.
<LI>Code 32-Exhaust Gas Recirculation (EGR) system failure-required change in air/fuel ratio not detected during diagnostic test.
Here's where I'd start if I were you-- The common denominator seems to be that you have a bunch of sensors not reading the way they should and you have an IAC motor that may be shorted or open.
The various sensors (except the O2 sensor) use a reference voltage supplied by the PCM. If the IAC motor is shorted, it could mess up the reference voltage. Use your wiring diagram to tell you what wire to the TPS is the reference voltage wire. Pull the TPS connector and with the key in the "run" position so everything's powered up, check the reference voltage with the pos lead of a volt meter to the reference wire and the neg lead to a good vehicle ground (even the battery neg). It should read about 5v. If it does not, pull the IAC connector--disconnect the IAC-- and see if anything changes. (You can also do a resistance check of the IAC to see if it's shorted, but the reference voltage test would confirm the "theory" of the effect of the short on other sensors.)
