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1998 Plymouth Neon 145,000 + miles DOHC mtx 2door no mods
Could not reset the code so –
Scanner gave battery temp – 5 V and 144 degree F Charging at 13.2 – 13.7
Changed the battery to a known good one after the scanner gave me a 11.8 V reading 2 minutes after key turned off after a 75 mile trip home from work for the wife.
Scanner gave battery temp – 5 V and 62 degree F after battery change
Charging is at 13.2 – 13.7So I don’t think the battery is the problem and I will put the one that I removed back in tomorrow.
Wiring seems to be in good shape. Battery terminals were cleaned recently and still good.Alternator?
Battery temp sensor? Anyone got a good one they don’t need and want to sell? (contact info below in my signature)Any suggestions?
How does the battery temp sensor work and where does it get information to display these readings?
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See if this helps John. 😉
I won’t have access to the vehicle until this weekend but I plan on putting the battery I removed back in. It’s not bad. I think that the high battery temperature readings of 5 V and 144 degrees F caused the battery charging voltage reading to be lowered. I guess when the PCM sees this it puts the charging system into a “limp mode” and reduces the charging voltage to the battery. I had been seeing a charging voltage previously of 14.1 – 14.7 before this occurrence. Then when the SES lamp and P1492 appeared, the charging voltage dropped to 13.2 – 13.7
My battery temperature sensor is not connected to the bottom of the battery tray as it should but there has never been a problem until now. It hangs down and farther away from the battery than it should be and if anything it should indicate a colder temperature than what it actually would be if it were correctly in place. I think the problem may be corrosion in the sensor connector, as I have had a problem with the ECT sensor connector being corroded and causing the temperature gauge to show readings of normal, then go to a position of sitting back on the off position pin, to very hot all in a matter of a few minutes. One of the connector wires of the ECT sensor pigtail ties into the ground side of the battery temperature sensor which is controlled by the PCM. This weekend I’ll have to get the T-pins out and do some testing and some contact cleaning to troubleshoot this further before making any purchases of parts I don’t already have to fix the problem.
Just picked up a used connector for the ECT sensor to replace the one I have on the vehicle now that I could not remove all the corrosion from. Will try and get it soldered into the wiring harness and shrink tubed this weekend also.
Thanks for the link C MProblem is solved, but only temporarily fixed. The battery temperature sensor for this vehicle has a plastic threaded part which is molded into the sensor case to allow a steel 3/4 nut to attach the sensor to the battery tray. This threaded plastic part of the sensor also protects the thermistor (heat activated resistor which changes its resistance depending upon the heat it senses) in the sensor. This threaded part was broken when I bought the vehicle but the sensor had a completed circuit up until the day this was posted. It seems that one of the leads to the thermistor broke and opened the battery temperature sensor circuit and so the battery light, SES and P1942 code came about which could not be reset and charging went into “limp mode”.
[IMG]http://imageshack.us/a/img854/583/neon19981996batterytemp.jpg[/IMG]
Today I removed the sensor, which needs to be replaced, and tested it for resistance and found none. Hence an open circuit. I found a broken lead at the thermistor and soldered it (note the sensor on the left, just under the blue thermistor the lead on the left has a silver ball of solder where I reconnected the lead to the thermistor). Checked the resistance with an Ohm meter and now found the 9 K Ohms that was missing when I first checked.
I plugged it back into it’s socket, Plugged in the MT2500 scanner and turned on the vehicle. The indicator lights on the dash cluster were no longer illuminated and the P1942 code was gone. The Battery Temperature Voltage went from 5 V to 2.8 V and the Battery temperature went from 144 degrees F to 39 degrees F as measured by the scanner. The vehicle running charge voltage went up to 14.1 – 14.4 (from 13.2 – 13.7) and was no longer in its “limp mode” and the charging system was now working as it should should.
As stated earlier the fix is just temporary as I have another sensor coming to replace this one. Proper troubleshooting and spending money on the tools to do the job rather than throwing the money at parts that do not fix the problem save a whole lot of time. I probably could have put a new alternator, battery and who knows what else into trying to fix this but instead it will cost about $10 for the used part and I know when it arrives it Will fix the problem. What I saved will have paid for some of the tools I’ve invested in.Hope this thread helps someone to save some time and money too.
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