|1986-1988 2.5L VIN U TBI
||Oxygen sensor voltage stays between 0.35 and 0.55 volts for 3 seconds
during closed loop operation and will set code after 40 seconds for
Century and Cutlass Ciera. For the Lumina, the oxygen sensor voltage
stays between 0.35 and 0.55 volts for 60 seconds during closed loop
operation and will set code after 2 minutes. Both systems can go into
open loop after 15 seconds.
||Coolant temperature sensor signal indicates a temperature of over
275° F for 3 seconds.
||Coolant temperature sensor signal indicates a temperature colder than
-22° F after the engine has been running for 2 minutes.
||TPS voltage was above 2.5 volts for 2 seconds when the MAP sensor
signal showed manifold vacuum to be 15 pounds or more under 1800 RPM.
||TPS voltage was under 0.2 volts for 2 seconds when the engine was
||Inlet ATS signal showed an air temperature of -22° F after the engine
has been running for 1 minute.
||Vehicle Speed Sensor Sensor/Circuit. Throttle position signal was
less than 2% with engine speed between 1400 and 4400 RPM and the MAP
signal showed low voltage and high manifold vacuum. Transmission was
not in park or neutral.
||Inlet ATS signal showed an air temperature over 275° F for more than
2 seconds after the engine has been running for 5 minutes and vehicle
speed was greater than 44 MPH.
||EGR open command did not change the fuel mixture when the command
was given during off idle operation. EGR opening should cause the mixture
to be slightly richer because of the low oxygen content of exhaust gas.
||MAP sensor signal voltage was too high (low vacuum) for at least 5
seconds when throttle opening was under 2%.
||MAP sensor signal voltage was too low (high vacuum) when engine speed
was under 1200 RPM or when engine speed was over 1200 RPM with throttle
opening was over 20%.
||Idle speed was over 150 RPM outside the desired engine speed commanded
by the ECM.
||The EST signal did not change when the ECM applied bypass voltage
to the ignition module.
||Oxygen sensor voltage was under 0.2 volts for 60 seconds of closed
||Oxygen sensor voltage was above specification. Century and Cutlass
Ciera was over 0.75 volts for 50 seconds in a closed loop. Lumina was
over 0.7 volts for 30 seconds and throttle angle was between 3% and
||Charging system voltage was greater than 16.9 volts for more than
50 seconds. Repair charging system.