SES light no codes, scanmaster not reading, car running rich


New Member
Dec 19, 2010
Hi there, so I just installed a new motor into my turbo t. Upon start up the engine will run after I give it a bit of throttle. It runs but has a high idle around 1500-2000rpm. The car is running very rich. Once I shift into drive rpms drop to where they should be until I put car in park again. The car also has a ses light on all the time. I have my scanmaster hooked up correctly and it turns on and then goes blank. Cannot get any readings.. If I do the paper clip trick the ses light stays lite but dims slightly and I can make out the reading 12-12-12 etc.
What I have checked
I have checked the main 7 grounds which l relocated to the intake with a stud, also the transmission ground is relocated to the intake with stud. The main ground off battery is good, the orange power lead off battery to ecm is good. I have another GN that I swapped it's ecm into the turbo t and ses light comes on almost right away. Did the same with the chip. I have checked all the fuses nothing is blown. I have checked and rechecked the the cam sensor it seems good and correctly setup. I replaced the o2 sensor the coolant sensor and same thing. The maf is a lt1 and the translator is setup correct. I replaced the coil pack with a spare I had and same thing and it's grounded correctly. The tps sensor was set up for my motor before it blew I haven't touched that. The egr valve has been delete and intake has been welded.
Details on motor,
42 pound injectors
Turbo tweak chip
Lt1 maf
Mild cam
Bigger turbo
3" downpipe
Find someone smarter than me to tell you how to get it out of diagnostic mode. Maybe a short in the ALDL connector.


Trouble Code 12 is a special case code that is not logged into the ECM's Non-Volatile Memory (NVM) when detected. When the ignition is "ON" and the ECM detects no ignition reference pulses coming from the ignition module, it illuminates the Service Engine Soon lamp.

Code 12 is also used when the ECM is in Diagnostic mode (ALDL Terminal B grounded, key On, engine Off) to signal the beginning or end of a so-called 'diagnostic sequence'. This is when the ECM enunciates each stored code using the instrument panel Service Engine Soon lamp.

When in this mode, the ECM will begin by flashing code 12 (on the lamp) 3 times. This indicates the beginning of a diagnostic sequence. It will then flash any codes stored in NVM 3 times each before proceeding to the next code. When all stored codes have been displayed, the ECM will again flash code 12 to indicate the end of the diagnostic sequence. The cycle continues as long as the ECM is in Diagnostic Mode.

NOTE: The codes will not be displayed in order of occurrence but rather in numerical order.