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Chevy expert
Chevy expert, ASE Certified Technician
Category: Chevy
Satisfied Customers: 10370
Experience:  30 yrs experience ase cetified tech shop owner
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Chevrolet c1500 this evening my 1989 Chevy Silverado C1500

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this evening my 1989 Chevy Silverado C1500 with a 5.7 v8 gave me a series of check engine lights on and off. I read the codes and it is giving me multiple different errors. 21 Throttle position sensor (TPS) - signal voltage is high during engine idle, 22 Throttle position sensor (TPS) is low during engine idle or fuel cutoff relay circuit- open or shorted to ground, 34 Mass air flow (MAF) sensor- signal voltage or frequency is low during engine cruise or Manifold absolute pressure (MAP) sensor - signal voltage is low during ignition on, 42 Electronic spark timing (EST) circuit- open or shorted to ground during engine run, and finally 44 Lean exhaust indication- oxygen (O2) sensor voltage stays low after one or two minutes of engine run:(left sensor on dual sensor engines). Is there possibly one issue causing all these to pop at similar timing, or are they separate? And what are some suggestions to fix these?
Submitted: 6 years ago.
Category: Chevy
Expert:  Chevy expert replied 6 years ago.
Welcome to just I'm here to help you and your 100% satisfaction is my goal.With this combination of codes you may have a faulty ecm or a faulty grounds to the sensors Check the Throttle Position Sensor voltage on the scanner and with a voltmeter. If they don't agree, check the Blue TPS wire at the Engine Control Module If voltage on the scanner and voltmeter agree, check for 5 volts to the TPS and a good ground to the TPS. If OK, sweep the TPS. If it has spikes or glitches, replace it.