H72 code thrown..What are causes?
Thread Starter
Burning Brakes
Joined: Mar 2004
Posts: 1,108
Likes: 4
From: Plano Texas
H72 code thrown..What are causes?
I've done a lot to my 94 including replacing some of the sensors, egr valve, cats, O2 sensors, etc. to get it ready to pass Texas emissions inspection. All seems good and the engine runs fine, BUT I get a 42 and 72 codes when I jumper the ALDL connector. The 42 code says the ICM is shorted or grounded (it's new) and the 72 code references no signal from the speed sensor. I know the ICM could be bad, although it is new, but is there anything else that would be obvious I could look for?
I read on a Corvette Central tech article that the 72 and 74 codes could be thrown because I replaced the radio head unit with an aftermarket one. If that's the case, how do I fix? They talk about adding resistors to some wires at the rear of the stock head unit, but it is now long gone as the car had a cheapo head unit in it when I bought it. Any suggestions?
Thanks in advance.
Mark
I read on a Corvette Central tech article that the 72 and 74 codes could be thrown because I replaced the radio head unit with an aftermarket one. If that's the case, how do I fix? They talk about adding resistors to some wires at the rear of the stock head unit, but it is now long gone as the car had a cheapo head unit in it when I bought it. Any suggestions?
Thanks in advance.
Mark
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
Check this link for the service bulliten on codes 72 & 74.
http://www.corvetteforum.net/c4/dave8476/index4.shtml
I might also consider cleaning the connector contacts on the ICM, coil and PCM. Look at the wires and make sure things get plugged in well.
Not exactly sure what kind of feeedback the PCM looks at to set the code. This seems to be a common asked symptom and question.
http://www.corvetteforum.net/c4/dave8476/index4.shtml
I might also consider cleaning the connector contacts on the ICM, coil and PCM. Look at the wires and make sure things get plugged in well.
Not exactly sure what kind of feeedback the PCM looks at to set the code. This seems to be a common asked symptom and question.
