Chris Etemadi

I got the codes from my computer and got 15 and 42. I was wondering If that could cause my car to have surging problems and it dies when i come to a stop frequintly. Also my car cuts out at 4000 rpm really bad all the way up after 4000 at WOT. And there is more after in the moring when the car is cold i have to let it warm up or it will bog like crazy and somtimes kill it when i try even medium acceleration. please help i need my car together soon before it gets too cold!
BTW i replaced my Coolant sensor about 8 months ago and i put teflon tape around it would that cause it not to ground?

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91 Z28 5.7l Camaro
T-56,McLeod Street Clutch, Cross Drilled Brakes, KYB's,AFPR, 3.73 Gears, Borla Adjustable Cat Back, Hypertech Chip, Hooker Headers.
more to come....
My 91 Z28

deadbird

I posted this a while back on the Electronics board for someone..

Diagnosis w/o a scanner - Code 15 indicates the the ECM is seeing a high voltage on the wire to the CTS (the yellow wire)

Clear the codes & run the engine until the Check Eng Light comes back on. Does code 15 return ? If not , then the problem is intermittant & no repair is needed at this time.

If the code 15 returns, clears the codes, disconnect the CTS & and install a jumper between the terminals of the CTS (usually yellow & black wires). Start the engine & run until the Check Eng Light comes back on. Then pull the codes. Is there a Code 15 or 14 ?

If there is a code 14, the coolant sensor wiring harness is OK. Check the connection to the coolant sensor. Check the resistance in the coolant sensor. If both are OK, then replace the ECM.

If there is a code 15, the wiring harness has an open circuit. Clear the codes. Connect a jumper wire from the yellow wire of the sensor harness to the block ground. Start the engine & run until the Check Eng light comes back on. Pull the codes. If code 14 comes up, inspect the black wire on the harness for an open. If 15 comes up, inspect the yellow wire on the harness for an open. If either 14 or 15 were generated but neither wire has an open circuit, replace the ECM.

Code 42 is this..

Code 42 Clear the codes, then run the engine to confirm that the condition that caused the code to set still exists. If the code returns, probe the tan and black by-pass wire with a voltmeter at the ECM If the voltmeter reads zero volts, disconnect the timing set connector an note the voltage. If the voltmeter continues to read zero volts, then inspect the tan and black wire to the ECM. If the wire is OK, replace the ECM.

If, when you disconnect the set timing connector, the voltage increases to 5 volts (w/engine still running), inspect the tan and black wire to the ignition module. If the wire is good, replace the ignition module.

When you originally probed the tan and black wire with the engine running, if there was 5v on the wire, connect a digital dwell meter to the white EST wire. Note the dwell reading. If the dwell meter reads anything other than 0 or 90 on the four cylinder scale, rev the engine. If the dwell changes, connect a timing light to the engine and note timing changes as the engine is revved. If the dwell changes and the timing changes, replce the ECM. If the dwell meter reads 0 or 90, replaec the ignitino module.

Hope that's of some use to you.



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RedFirebird

The coolant sensor is not grounded to the engine because if it was it would be very innaccurate. You will notice it has 2 wires going to it. If you want to test the sensor warm up the engine and put an ohm-meter to the connections on the sensor. record the coolant temperature at the time you are testing it. I don't have a table right here but i'm sure you can do a search and find one to see what the resistance should be @ specific temps. Your readings should be close. If the coolant sensor is good, test the wires going from the wiring harness to the sensor. put a voltmeter up to the connector. if it isn't any kind of voltage, you have a short or loose wire which will cause it throw a code 15.

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Red '87Formula Firebird
-mostly stock 5.0L LG4 w/cowl induction setup borrowed from '83 TA and T5 tranny.

My newest Ride:

'85 Silver L98 Corvette w/4+3 manual tranny. not bad for $3500.

Chris Etemadi

thanks for your help guys. I will check it out towmorrow

quattroboy

Sounds all too familiar!

Turned out to be my ECM.

See if you can swap your ECM for a known good unit so that you can test out if it is the computer also try swapping the prom if appropriate.

Make sure the unit serial number of the ECM is the same or compatible though.

You would be surprised what a faulty ECM can do to your wheels!