Code P0158 1994 Mercury Topaz

1994 Mercury TopazI bought my 1994 Mercury Topaz V4 Automatic about a month ago. Once I pulled the codes and it had a code P0158 for the MAF sensor. I replaced the MAF sensor, air filter, PCV, and fuel filter. When I was on the freeway today and I noticed it was making this exaggerated revving sound after 60 mph. Then it slowly and consistently lost speed. I immediately got off the freeway in time to coast into the gas station as it cut off. Then when I tried to restart it, it won’t turn over. Help!


Won’t Turn Over

The good news is I do not think the MAF sensor you installed has anything to do with the engine not turning over. The issue you described sounds like the alternator is no longer charging the battery and the engine ran off the battery for as long as it could and then quit. A dead battery is the most common reason for an engine not to turn over. However there are other possibilities. You’ll find a no start diagnostic chart to follow from this page.

Mercury Code P0158 – O2 Sensor Circuit High Voltage Bank 2 Sensor 2

P0158 Ford Description

The heated oxygen sensor 2 (HO2S), after three way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank. For optimum catalyst operation, the air fuel mixture (air-fuel ratio) must be maintained near the ideal stoichiometric ratio. The HO2S output voltage changes suddenly in the vicinity of the stoichiometric ratio. An Engine Control Module (ECM) adjusts the fuel injection time so that the air-fuel ratio is nearly stoichiometric. The HO2S generates a voltage between 0.1 and 0.9 V in response to oxygen in the exhaust gas. If the oxygen in the exhaust gas increases, the air-fuel ratio becomes Lean. The ECM interprets Lean when the HO2S voltage is below 0.45 V. If the oxygen in the exhaust gas decreases, the air-fuel ratio becomes Rich. The ECM interprets Rich when the HO2S voltage is above 0.45 V.

Code P0158 Possible Causes

– Faulty Rear Heated Oxygen Sensor Bank 2
– Rear Heated Oxygen Sensor Bank 2 harness is open or shorted
– Rear Heated Oxygen Sensor Bank 2 circuit poor electrical connection
– Inappropriate fuel pressure
– Faulty fuel injectors
– Intake air leaks
– Exhaust gas leaks