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Lee, ASE Certified Technician
Category: Chevy
Satisfied Customers: 395
Experience:  31 years experience ASE Master Technician
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1998 chevy blazer: Doing diagnostics..EVAP..Control System..Leak

Customer Question

Doing diagnostics on a 1998 chevy blazer got these:
P0442 EVAP Emission Control System Leak (Small) and
P1870 Manufacture control transmission

Anyone know what these mean?
Submitted: 7 years ago.
Category: Chevy
Expert:  Lee replied 7 years ago.
Hi! There

For both codes clear and see if they come back, If they do then:
For the P0442: Check the fuel tank cap to make sure it is tight and is sealing good. Then clear code and see if if comes back. If it does come back after 2 cold starts, then you will need to hook a smoke machine to the evap system to find the leak. As for the P1870 This is a transmission component slipping. hook up a monitor to the system and drive the blazer at 45 to 60 mph and check the speed sensor compared to the output shaft speed sensor. they should be about the same reading when trans is locked up. Poss. cause for this code is faulty sensor. either veh. speed sensor or output speed sensor. Unless you have a monitor or other test equip. this code would be better to take to the repair shop.

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Customer: replied 7 years ago.
Lee, thanks for the information. At least now I know what to talk to me tech about.
Expert:  Lee replied 7 years ago.
You are welcome. Thank You for using Just Answers.