5.3 swap issues
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From: Illinios
5.3 swap issues Ok little bit of back ground did 99 5.3 swap into a 1953 chevy 210 had factory harness cut and computer tuned cars been up and running couple weeks but not right no dtcs but is showing intake air temp at 311° when I unplug maf it drops to 120° I've replaced it with a known good unit the Temps will vary but are never correct I've traced wiring I've moved grounds from block directly to battery car idles and runs ok ish with maf unplugged but not correctly at a loss hope some on here can help
Thread Starter
Teching In
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From: Illinios
I'm suspecting a bad pcm I've tried 3 maf all gave me different iat reading one was off my dd so I'm 90% sure it's good I've replaced the plug and checked wiring about a foot into harness
You really need to measure the resistance of the wire from iat to the pcm. The sensor is a thermistor, as temp goes up resistance goes up as temp goes down resistance goes down. The wire may appear fine visually but be broken inside the insulation, you really can only test it with a ohm meter. Should be less than 1 ohm, really less than 0.5 ohm.
With the sensor unplugged it should read -40*, with it showing 120* theres resistance in the circuit somewhere. If you dont have a dvom i would inspect the wire at the pcm, ive seen them back out of the connector and give false readings. If the pin looks fine remove that wire from the connector. With it removed from the pcm connector the pcm should show -40*. If it still reads 120* or something besides -40* then the pcm is bad.
With the sensor unplugged it should read -40*, with it showing 120* theres resistance in the circuit somewhere. If you dont have a dvom i would inspect the wire at the pcm, ive seen them back out of the connector and give false readings. If the pin looks fine remove that wire from the connector. With it removed from the pcm connector the pcm should show -40*. If it still reads 120* or something besides -40* then the pcm is bad.
Thread Starter
Teching In
Joined: Sep 2013
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From: Illinios
Unplugged ecm and plugged in another stock ecm temps are reading what they should so it's a bad pcm my question is isn't this something the guy should have seen when going there the ecm I'm not trying to point fingers just a question
