Help with a 15 error code
Thread Starter
Drifting
Joined: May 2002
Posts: 1,546
Likes: 5
From: Sacramento California
Help with a 15 error code
Hi, I'm posting this question for a friend who has been trying to solve this annoying little problem.
Here is the history. 1985 coupe, he replaced the valve cover gaskets and after completion it threw a check engine light, code 15 (temp sensor high) so we replaced the one in the intake (ecm) and the left bank (gauge?) The right bank sensor was fairly new so it was not replaced. Checked all wiring and connectors, (several times), disconnected that battery for @ 5 min. (Trying to clear the code) Still gets the code 15. The main fan runs constantly and the car runs like poop until it is warm. What are we missing here? Is there something else that might be causing this problem? I'm an early C3 guy and am still learning about the electronic functions of newer cars so any help would be appreciated.
Thanks
Mick
Here is the history. 1985 coupe, he replaced the valve cover gaskets and after completion it threw a check engine light, code 15 (temp sensor high) so we replaced the one in the intake (ecm) and the left bank (gauge?) The right bank sensor was fairly new so it was not replaced. Checked all wiring and connectors, (several times), disconnected that battery for @ 5 min. (Trying to clear the code) Still gets the code 15. The main fan runs constantly and the car runs like poop until it is warm. What are we missing here? Is there something else that might be causing this problem? I'm an early C3 guy and am still learning about the electronic functions of newer cars so any help would be appreciated.
Thanks
Mick
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
The coolant temp sensor for the ECM is under the TB in the front of the intake base.
Since this sensor has a negative temp. cooeficient the code 15 indicates that the resistance is too high, or an open circuit.
The problem could be due to a bad sensor, a bad connector, an open in the wire or a bad ECM input.
Remove the connector from the sensor and jumper the Yel & Blk wire pins and start the engine. After a few minutes the ECM should set a code 14, indicating that wiring and ECM input are OK.
Since this sensor has a negative temp. cooeficient the code 15 indicates that the resistance is too high, or an open circuit.
The problem could be due to a bad sensor, a bad connector, an open in the wire or a bad ECM input.
Remove the connector from the sensor and jumper the Yel & Blk wire pins and start the engine. After a few minutes the ECM should set a code 14, indicating that wiring and ECM input are OK.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
The sensor in the left head, is indeed the sender for the gauge in an '85. The similar device in the other head is a fan switch for the auxiliary fan, if your car is so equipped. One thing to keep in mind on these computer cars, is that a "code" merely signifies that an "out of bounds" reading was sent to the ECM. By "out of bounds", I mean a reading that doesn't match up with the other readings it is receiving. Of course, a faulty sensor will send incorrect data, but it is also possible that a malfunction of "something else" caused the sensor to correctly relay, information that was caused by some other problem. It pays (in not replacing good parts) to test the sensor for correct operation, before condemning it. If the sensor is OK, as it appears in your case, you can move on and test other items, rather than "throw money", blindly at a problem. A great investment is the Factory Service Manual, printed by Helm Inc. You can get your own at www.helminc.com. It has great trouble shooting charts for tracking down problems, in a logical sequence.
RACE ON!!!
RACE ON!!!
Thread Starter
Drifting
Joined: May 2002
Posts: 1,546
Likes: 5
From: Sacramento California
Hey Thanks guys, It was an "Open" The connector to the sensor had one of the connectors pushed back into the housing. A little tweaking and now it has a good solid connection. 
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by 427basketcase
Hey Thanks guys, It was an "Open" The connector to the sensor had one of the connectors pushed back into the housing. A little tweaking and now it has a good solid connection.
RACE ON!!!
