94 coolant temp sensor code 15
Thread Starter
Instructor
Joined: Apr 2011
Posts: 209
Likes: 31
From: east of dallas
94 coolant temp sensor code 15
I have had my 94 (96k miles)for a year next month and have been able to fix any problem i have come across, thanks to the information i have gotten from other threads, but i am stumped by my current problem.
Ok i have a constant reading of 142 degrees f. on my digital display and a service soon light on display , analog gauge works fine. the car is hard to start (tries to flood)
Ok i pulled codes i get a module 1 code 41, module 4 code 15, module 9
code 72, i think the main problem is the code 15 which is coolant temp sensor voltage high--trouble shooting i installed new senor from gm--jumpered plug got code 14 (wires are good)--checked 10mm ground for ecm -bought another sensor no change-only thing i have not done is change thermo stat, but my digital gauge never changes always 142 no matter what any time of the day,
I would never take her to the shop without a exhausting my options, but i am getting close, car drives good just is hard to start, and just installed new plugs and wires what a b***
Ok i have a constant reading of 142 degrees f. on my digital display and a service soon light on display , analog gauge works fine. the car is hard to start (tries to flood)
Ok i pulled codes i get a module 1 code 41, module 4 code 15, module 9
code 72, i think the main problem is the code 15 which is coolant temp sensor voltage high--trouble shooting i installed new senor from gm--jumpered plug got code 14 (wires are good)--checked 10mm ground for ecm -bought another sensor no change-only thing i have not done is change thermo stat, but my digital gauge never changes always 142 no matter what any time of the day,
I would never take her to the shop without a exhausting my options, but i am getting close, car drives good just is hard to start, and just installed new plugs and wires what a b***
Thread Starter
Instructor
Joined: Apr 2011
Posts: 209
Likes: 31
From: east of dallas
the other codes are module 1 --(41) loss of pcm serial data comuunications and module 9-- code (72)--serial data link fault
but everything else works fine so ccm and pcm must be communicating
but everything else works fine so ccm and pcm must be communicating
Le Mans Master
Joined: Jan 2006
Posts: 6,564
Likes: 6
From: Woodstock Georgia
The one on the passenger side head is for the analog gauge only. You are troubleshooting the correct one, the one on the water pump. If it is faulty or the wires are crossed (shorted) the ECM thinks the ambient temp is like 40 below and the car will be very rich, hard to start and run like crap. It will smooth out and run better when it goes into closed loop.
Le Mans Master
Joined: Jan 2006
Posts: 6,564
Likes: 6
From: Woodstock Georgia
It sounds like nothing more than either a bad, or wrong, sender or crossed wires. The 94 ECM and CCM very, very rarely go bad. Actually in 94 the ECM became know as a PCM (powertrain control module) since it also controls the electronic A4 transmission (4L60E). I would check the sender wires close to the sender for a possible short.
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Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
The 15 simply means the Sensor or ground is open - ie, reference voltage isn't reaching ground. PCM sends 5 volts to the Sensor. Sensor resistance, which decreases with Temperature, causes that voltage to drop. PCM uses the drop to calculate temperature. At low temperatures, the drop is less, PCM senses more voltage; high temperature less voltage. The 15 is telling you there's no drop and the PCM is sensing the reference or 5 volts.
You've all ready verified that the wiring is good by generating the 14 and you've replaced the Sensor. That leaves the Connector or the PCM. Aftermarket Sensors usually come with a new Pigtail or NAPA sells weatherpaks (connectors). If replacing the Connector, crush the old one with some pliers, then reform any locking tangs on the wires and insert into the new Connector. Make sure the female ends of the connectors haven't been spread apart from whatever you've stuck in it to generate the 14.
You've all ready verified that the wiring is good by generating the 14 and you've replaced the Sensor. That leaves the Connector or the PCM. Aftermarket Sensors usually come with a new Pigtail or NAPA sells weatherpaks (connectors). If replacing the Connector, crush the old one with some pliers, then reform any locking tangs on the wires and insert into the new Connector. Make sure the female ends of the connectors haven't been spread apart from whatever you've stuck in it to generate the 14.
Thread Starter
Instructor
Joined: Apr 2011
Posts: 209
Likes: 31
From: east of dallas
havent changed plug yet but while car was running i plugged and unplugged temp unit and could hear engine tone change, wonder if pcm unit is problem with my climate control also
Le Mans Master
Joined: Jan 2006
Posts: 6,564
Likes: 6
From: Woodstock Georgia
The 15 simply means the Sensor or ground is open - ie, reference voltage isn't reaching ground. PCM sends 5 volts to the Sensor. Sensor resistance, which decreases with Temperature, causes that voltage to drop. PCM uses the drop to calculate temperature. At low temperatures, the drop is less, PCM senses more voltage; high temperature less voltage. The 15 is telling you there's no drop and the PCM is sensing the reference or 5 volts.
You've all ready verified that the wiring is good by generating the 14 and you've replaced the Sensor. That leaves the Connector or the PCM. Aftermarket Sensors usually come with a new Pigtail or NAPA sells weatherpaks (connectors). If replacing the Connector, crush the old one with some pliers, then reform any locking tangs on the wires and insert into the new Connector. Make sure the female ends of the connectors haven't been spread apart from whatever you've stuck in it to generate the 14.
You've all ready verified that the wiring is good by generating the 14 and you've replaced the Sensor. That leaves the Connector or the PCM. Aftermarket Sensors usually come with a new Pigtail or NAPA sells weatherpaks (connectors). If replacing the Connector, crush the old one with some pliers, then reform any locking tangs on the wires and insert into the new Connector. Make sure the female ends of the connectors haven't been spread apart from whatever you've stuck in it to generate the 14.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Re ground - it's the black wire and spliced into the TPS and MAT on most GM'S. If it were open beyond the splice, you'd get Codes for those Sensors too. If it was open before the splice, it wouldn't generate the 14.
Thread Starter
Instructor
Joined: Apr 2011
Posts: 209
Likes: 31
From: east of dallas
yes i agree it is not the black wire, but the yellow is c25 at the pcm, i was gonna pull plug and check connectivity, looks like you pull the connector that they call clear and go to pin 25, after disconnecting battery and being careful not to have any static electricity
Thread Starter
Instructor
Joined: Apr 2011
Posts: 209
Likes: 31
From: east of dallas
found the problem, there was a bad connection where the wires splice together for all the components (black wire) threw me off because i was getting a code 14, which means wires are good, the splice is about a foot back in main wire loom, thank you for the help guys, case closed, glad i didn`t buy the pcm, found the problem while bugging connection at pcm from cts