Check engine light on?

Good morning.

Here is the test for the knock sensor for code 52.

Roy

1. Warm-up engine to normal operating temperature.
Tachometer Hookup
imageZoom/Print

2. Attach a timing light with advance indicator and a tachometer.

Fig. 223 Ignition Timing (10)
imageZoom/Print

3. While operating the engine at 2,000 rpm, check the ignition spark advance and calibrate the timing mark to 0° TDC.
4. Using a wrench or small hammer, tap the exhaust manifold and observe the timing marks.
5. The ignition timing mark should move in the retard direction, depending on the intensity and speed of the tapping.
6. If the timing mark does not retard, turn the engine off and check the wiring between the Knock Control Sensor and the ECU.
Locate the Knock Control Sensor, (on the top, center of the engine block), and ensure that the connector is secure.
7. If no problems are found, replace the Knock Control Sensor and repeat test procedure.
8. If timing still does not retard, replace the ECU.
9. Disconnect timing light and tachometer from the engine.

Check the fuel pressure if okay -clean out the idle air control valve and test the throttle position sensor-

Try removing the EFI fuse to clear the CEL if not pull the code/s by jumping Te-1 to E-1 in the diagnostic connector-this is your starting point of diagnosis this guide will help

https://www.2carpros.com/articles/toyota-trouble-code-definitions-and-code-gathering-method-1990-1995

Please run down this guide and report back.

That code indicates there is no signal from the vehicle speed sensor. Check for wiring issues at the sensor and if everything is good, replace the sensor.

That code indicates there is no signal to the ECU from the vehicle speed sensor. If there are no wiring issues, replace the sensor.

HI
Find test connector near fuse box key on jumper wier from TE1 to E1. Check engine light will flash see diagram on how to read

Then post codes will advise. Wires to O2 neeed to soildered any increased resistence can cause trouble.
Thanks for donate

Hi boxster617,

This guide can help you

https://www.2carpros.com/articles/toyota-trouble-code-definitions-and-code-gathering-method-1990-1995

Please run down this guide and report back.

Diagnostic Trouble Codes - 1990
Toyota
11 ECU Power Supply.
12 Engine RPM Signal.
13 Engine RPM Signal.
14 Ignition Signal.
21 Oxygen Sensor (OS) Signal.
22 Water Temperature Sensor (THW) Signal.
24 Intake Air Temperature Sensor (THA) Signal.
25 Air/Fuel ratio lean.
26 Air/Fuel ratio rich.
27 Sub-oxygen sensor signal.
31 Air Flow Meter Signal.
32 Air Flow Meter Signal.
41 Throttle Position Sensor (TPS).
42 Vehicle Speed Sensor (VSS) Signal.
43 Starter Circuit Signal.
51 Switch Condition Signal.
71 EGR system malfunction.

Four wire o2 sensors actually breathe through the plastic wire insulation, o2 sensors are very cheap and I recommend replacing it if you spliced wires. This sensor will adversely affect fuel economy and if it shorts out can ruin the PCM. Very expensive fix then! Once of prevention is worth.

Hello,

The check engine may have been on before and the light was burnt out. When you replaced the light bulbs it showed up. If the vehicle has a hard code the light will stay on until fault is corrected. The emissions codes like the evaporated system with have a error and the vehicle will function normally. Regardless you need to check the diagnostic trouble codes and here is how you do it. Turn the ignition switch to on. Do not start the engine. Connect terminals TE1 and E1 of the check connector located near the No.2 relay block schematic is showed below. Read the diagnostic code as indicated by the number of flashes of the "Check Engine" warning light. Normal system operation the light will blink 2 times per second. . Malfunction Code Indication the light will blink a number of times equal to the malfunction code indication with a 2.4 second interval between each code indication.After all codes have been output, there will be a 4.5 second pause.

The code display will be repeated as long as both check engine connector terminals are connected. Hint: In event of a number of trouble codes, indication will begin from the small value and continue to the larger in order. After the diagnosis check, remove the service wire. Please check out the guide and schematics below. Pull all troubles codes and write them down in case they get erase by accident. Start diagnostics in the order each code is pulled. Repair the malfunction and erase and erase the codes.

Here is how the erase codes without a scan tool safely: Cancellation can also be done by removing the battery negative (-) terminal for 10 minutes, but in this case, other memory systems will also be cancelled out. If the diagnosis code is not cancelled out, it will be retained by the ECU and appear along with a new code in event of future trouble.If it is necessary to work on engine components requiring removal of the battery terminal, a check must first be made to see if a diagnostic code has been recorded. After cancellation, perform a road test to confirm that a "normal" code is now read on the check engine warning light. If the same diagnosis code appears, It indicates that the trouble area has not been repaired thoroughly. If you need more information how to diagnose the codes you pull. Please make another post and we will get it for you. Let us know if this information was helpful.

Thank you
Joe Terwilliger

https://www.2carpros.com/trouble_codes/obd2

How was this code retrieved, does it have an OBD connection?

It means "Open or short signal in vacuum switches signal VSW1, VSW2, VSW3" These are EGR solenoids.