How to fix code 13 rpm signal - 1990 Lexus LS 400

Depends on the vehicle.
On GM models, code 13 means you have a problem with the O2 sensor. But on Ford products you have a problem with the ignition or RPM signal.

Clearing the codes is simple that is done by removing the fuse of the EFI from junction box 2 for 10 seconds. Make sure to remove the jumper wire and switch the key off before clearing the codes.

Here are some common Lexus vehicles 1990-1995 codes:

Code 12 and Code 13 Rpm signal circuit fault
Code 14 Igniter signal circuit fault
Code 16 ECT control signal fault
Code 21 and Code 28 Main oxygen sensor fault (for ES300; SC300 & GS300 models)
Code 22 Coolant temperature circuit fault
Code 24 Intake temperature sensor circuit fault
Code 25 and Code 26 Air fuel ratio fault (for ES300 & SC300 models)
Code 27 Sub-oxygen sensor circuit fault (for ES300 CA & GS300 models)
Code 31 Low airflow meter voltage (for ES300 and GS300 models)
Code 32 High airflow meter voltage (for ES300 model)
Code 35 Barometric pressure sensor circuit fault (for GS300 & SC300 models)
Code 41 and Code 47 Throttle position sensor circuit fault
Code 42 Vehicle speed sensor circuit fault
Code 43 Starter signal
Code 51 Switch condition signal fault (for ES300; GS300 & SC300 models)
Code 52 Code 52 and Code 55 Knock sensor circuit fault
Code 71 EGR system circuit fault (for ES300; GS300 & SC300 models)
Code 78 Fuel pump control circuit fault (for GS300 & SC300 models)

1.6 GLi COROLLA

DTC NUMBER TROUBLE AREA 12 RPM signal 13 RPM signal 14 IGN signal 16 ECT Signal 21 Oxygen sensor signal 22 Water temperature signal 24 Intake air temperature sensor 25 Air / Fuel ratio lean 31 Vacuum sensor signal 41 Throttle sensor 42 Vehicle speed sensor 43 Starter signal 52 Knock sensor 51 Switch COND

Your going to have to repair the code 13 RPM signal loss issue first before the code would clear.

Chances are the problem causing the code to be set is still there.
If the problem is fixed, and you clear the code, it should not come back.
Code 13 should be a loss of RPM signal which could be a cam sensor or something else.

Lets start with - whats the make model and year ?
If it is a GM product, code 12 is system normal, 13 is a problem with the O2 sensor, 41 is a computer problem, and 43 is electronic spark control.
You could do a compression test to make sure all of the cylinders are normal as far as the valve train goes. Code 41 could cause the other codes and your performance issues.

The RPM signal comes from the crank sensor. The harness connector needs to be checked for a 5v reference signal and the ground side needs to be checked for a good ground. This test is to rule out the computer as being the issue. Then the signal wire needs to be checked for a good signal. When the crank sensor fails you get not spark and no fuel., You will need a waveform viewer to determine if the sensor has failed.
You will need a basic meter to determine if the computer has failed.

For 83-86 Camry, 87 corolla, 84-87 pickups and 4-runner: Code 12 = knock sensor or circuit (distributor or circuit on Cressida, Supra, and Celica 3S-GE)

87-90 Camry, all other models 88-90: Code 12 = Rpm signal/no NE or G signal to ECU within several seconds after engine is cranked.

All models from 1991 on: Code 12 = Rpm signal No "Ne" signal to the ECM within several seconds after the engine is cranked. No "G" signal to the ECM two times in Succession when engine speed is between 500 rpm and 4000 rpm.

CODE 13 NO NE IGNITION SIGNAL TO ECM WHEN ENGINE SPEED IS GREATER THAN APPROXIMATELY 1000 RPM. CODE 14 NO IG OR IGF IGNITION SIGNAL TO ECM FROM IGNITER SEVERAL TIMES IN SUCCESSION.

HOW TO FIX CODE 13 1995 LEXUS SC400