I have a 1993 chevrolet c10 half ton pick-up with a code 21 in the computer. i need diagnosis help with this?

Question

if anyone have a car diagnosis program and they could help me with this code i would really appreciate it. a lot

Answer 1

Chevy OBD1 codes for an s10, should be the same across the chevy board.

Here are some codes that you can use to get you started.

12 Diagnostic Mode
13 Oxygen sensor or circuit
14 Coolant sensor or circuit / high temperature indicated
15 Coolant sensor or circuit / low temperature indicated
16 Transmission speed error (4L60 or 4.3L "S" & "T" series w/ manual)
17 Crank signal circuit shorted or faulty ECM
18 Crank signal circuit open or faulty ECM
19 Fuel pump circuit short
19 Crankshaft position sensor (1988-1991 models)
20 Fuel pump circuit open
21 Throttle Position Sensor (TPS) circuit or plunger
22 Throttle Position Sensor (TPS) out of adjustment
21/22 Grounded wide-open-throttle (WOT) circuit at same time
23 Manifold Absolute Temperature (MAT) sensor or circuit / low temp.
24 Vehicle Speed Sensor (VSS) or circuit
25 Manifold Air Temperature (MAT) sensor or circuit / high temp.
26 Throttle switch circuit shorted
27 Throttle switch circuit open
31 Turbo over boost (Turbo models)
31 Canister purge solenoid circuit
31 Camshaft sensor or circuit
31 EGR circuit (1988 to 1990 TBI)
31 Shorted MAP sensor circuit
32 BARO sensor or circuit (carbureted models)
32 EGR circuit (fuel-injected models)
32 Open MAP sensor circuit
33 Manifold Absolute Pressure (MAP) sensor or circuit (low vacuum)
33 MAF (Mas Air Flow) sensor or circuit
33 Manifold Absolute Pressure (MAP) sensor signal voltage high
34 Manifold Absolute Pressure (MAP) sensor signal voltage low
34 MAF (Mas Air Flow) sensor or circuit
35 Idle Air Control (IAC) valve or circuit
35 Idle Speed Control (ISC) switch or circuit (shorted)
36 Mass Air Flow (MAF) sensor burn-off circuit
36 Closed throttle shift control (1991)
37 MAT sensor temp. high (1984-1986)
37 Brake switch stuck on (4L60-E transmission)
38 Brake Input Circuit (brake light switch)
38 MAT sensor temp. low (1984-1986)
38 Brake switch stuck off (4L60-E transmission)
39 Torque converter clutch
39 Knock sensor circuit shorted (4.3L, manual trans., "S" & "T" pick-up)
40 Power steering pressure switch circuit
41 No distributor signals to ECM, or faulty ignition module
41 Cylinder select error
42 Electronic Spark Timing (EST) circuit
43 Throttle Position Sensor (TPS) out of adjustment
43 Knock sensor signal
44 Oxygen sensor or circuit - lean exhaust
45 Oxygen sensor or circuit - rich exhaust
46 Power steering pressure switch (4 cylinder - air-conditioned modules)
46 Vehicle Anti-Theft System (VATS)
47 Air conditioning clutch and cruise circuit
48 Misfire diagnosis
53 System over-voltage (ECM over 17.7 volts)
53 EGR system (carbureted models)
53 Alternator voltage out of range
55 ECM/PCM error
55 Oxygen sensor circuit or ECM
56 Vacuum sensor circuit
58 PASS key fuel enable circuit
58 Transmission code - TTS high temp. (sensor or signal wire grounded)
59 Transmission code - TTS low temp. (sensor or signal wire open)
61 Oxygen sensor signal faulty
63 MAP sensor voltage high
64 MAP sensor voltage low
64 Right side oxygen sensor lean (dual sensor models)
65 Right side oxygen sensor rich (dual sensor models)
66 Air conditioning pressure sensor circuit
67 Air conditioning pressure sensor or clutch circuit (Chevrolet)
67 Cruise switch circuit
68 Air conditioning relay circuit (Chevrolet)
68 Cruise system problem
69 Air conditioning clutch circuit (Chevrolet)
69 Air conditioning head pressure switch circuit
69 Transmission code - Torque converter stuck on (4L60-E)
72 Gear selector switch (Chevrolet)
72 Transmission code - Vehicle Speed Sensor (VSS) signal loss (4L60-E)
75 System voltage low (charging system problem)
79 Transmission fluid temperature high (4L60-E)
81 Transmission code - QDM solenoid "A" (1st and 2nd gear) current error
82 Transmission code - QDM solenoid "B" (2nd and 3rd gear) current error
99 Power management, cruise control system

Answer 2

If the light is on all the time,its a hard code,if the light goes on and off its a soft code, either way 21 is throttle positioning sensor, or the circuit,you can either change it,or have it checked out,with a digital volt meter.

Answer 3

Code 21 is a throttle position sensor voltage too high. Sounds like the tps is shorted out.

Answer 4

take your truck to auto zone for a free code scan. they will print out solutions for the code 21 or other codes.

Answer 5

Are you sure it's not code 12? (no faults noted)

Answer 6

TPS failure was quite common for that model year. Even had a redsign released.

Answer 7

go to local parts store for free scan...in my town advance,autozone and o'reily do it free.