How to Fix Limp Mode & ETCs Error Codes on the 5th Gen 4Runner

Limp Mode – What is it, How Can it Happen, and How to Fix it

The back story: 

I jumped in the truck and had no throttle. At mid to full throttle, I had zero response. The RPMs were stuck at 1000 RPMs. The transmission would engage into first gear which was enough to “limp” close to home and even downhill, RPMs managed to take the 4Runner into second gear.

Uphill was not on our side though. I ended up having my girl come give me a tow home with our other 4Runner. Before requesting a tow home, I tried the basis of restarting, disconnecting the pedal commander, disconnecting the battery terminal for 5-10 min, etc.

Initial Troubleshooting

Also, Max (an author at Trail4R) called me to troubleshoot some other areas as well like moisture near the firewall, ensuring a tight gas cap and checking for bad wires, etc. Additionally, I had a bunch of guys (thank you all by the way) on Instagram who replied with multiple areas to check and consider like the MAF (mass airflow sensor), dirty throttle body, ECU fuses, ECTS fuses, etc.

I woke up the next morning, took a trip to Autozone, and bought a code reader (INNOVA 3030). Before we started scanning, we checked the MAF and it was clean, then we cleaned the throttle body and checked for any build-up around the inlet.

Finally, we checked the fuses:

• ETCS – engine fuse box
• ECU-B – engine fuse box
• ECU-IG No.1 – dash panel fuse box
• ECU-IG No.2 – dash panel fuse box

After checking the fuses, and cleaning the throttle body, we reset power to the battery again for good measure, let it sit disconnected for 10 minutes and then started the 4Runner again, we still had many indicator lights on the dash.

We had the following lights:

• Check Engine Light
• Trac Off
• Multi-Terrain Select (Crawl Control)
• BRAKE – even though the brake was not depressed

We pulled the following codes:

• P2118: Throttle Actuator Control Motor Current Range/Performance
• P2119: Throttle Actuator Control Motor Current Range/Performance
• P0123: Throttle Position Sensor/Switch ‘A’ Circuit High Input
• P2135: Throttle Position Sensor/Switch ‘A’  / ‘B’ Voltage Correlation

All of this was being documented on Instagram so we had a solid community of 4Runner owners and even a few Toyota Technicians giving us pointers.

Comments On Limp Mode

Try doing the easy first if you enter into limp mode – yaw rate calibration or zero point calibration. You have crawl control and not sure if you have downhill assist but do the whole thing. I will get you the official Toyota docs that will give you the how-to. Not saying for sure this is the issue but I have seen a zero-point do the trick when the Christmas tree comes on. My personal did that one day out of the blue. It was fine when I dropped my kid at school but when I left school and took off from the light I lost throttle and went into limp mode out of the blue. Limped to the shop and hooked up the pc (I have the full Toyota tech stream) and did the zero point calibration and fixed it immediately. No you don’t need the techstream and the general file will give you the info on how to. – Scott Fisher

Calibration was a good place to start as we just had a new alignment done (which could potentially cause limp mode) however, this was not the case for us. In case you want to attempt the zero point calibration, the step by step instructions is below.

If you are unfamiliar with the zero-point – here is another article with examples of why you may need to perform this calibration.

Troubleshooting Limp Mode on The 5th Gen 4Runner

Possible Problems (Start here): 

• Restart your 4Runner
• Disconnect the battery terminal for 10 min, then restart
• Disconnect the pedal commander
• Tighten your gas cap
• Check all codes
  • Code reader
• Clean the MAF (mass airflow sensor)
  • MAF cleaner
• Clean the throttle body
  • Throttle body cleaner (You can use MAF cleaner on a Throttle body but you can’t use throttle body cleaner on your MAF)
• Check Relevant fuses (ECU fuses, ECTS fuses, etc.)
  • Low profile fuses (great to have just in case)
  • Fuse tester
• Clean the wheel speed sensors
  • MAF cleaner
• Check wires near throttle body, gas pedal and all connectors
• Check connectors for corrosion
• Calibrate 4Runner (Standard, Crawl Control and DAC)

Because I have two 4Runners, I ended up swapping throttle bodies/actuators from one 4Runner to another. We also swapped gas pedals to see if there were issues there. Both of these parts turned out to be in perfect working order.

Below you will find comments from others that have had their 4Runners enter limp mode. These are all common reasons why your 4Runner might enter into limp mode and possibly how to fix the issue. Although these are a few of the most common, it doesn’t mean your exact problem is listed here. The main point here is to troubleshoot every area you can. It might take you 5 min, a day, a couple of weekends or in my case, you may end up taking it to Toyota.

Possible Causes of Limp Mode

Dirty wheel speed sensors:

I ran into a smaller version of the Christmas tree on my 13 4R. Ended up weirdly resolving itself. I believe it ended up being dirty wheel speed sensors. It was less of a limp mode though. I could get into the throttle halfway before it would accelerate. The full-throttle felt like 1/4 throttle. Reseated the Pedal commander. I believe that may have spoofed it into losing the Christmas tree but it came back soon after. I haven’t seen it since though.

Bad Wires Near the Throttle Body:

Shoot I had the same thing happen. It was a rat that chewed up one wire by the coil packs. And a second time was the throttle harness on the intake. A wire snapped.

Pedal Commander Problems:

I had the exact same problem with the pedal commander a few days ago. I disconnected that thing, left it in the garage for a day and the problem was gone. I just had my car serviced a day before this thing happened. I have not reinstalled the Pedal Commander but have read a couple threads on the forum where people have had lots of problems with the Pedal Commander throwing the 4Runner into Limp Mode. If this really is the issue – PC will send you out a replacement but no guaruntee it wont happen again. I probably wont ever run a throttle response controller agian after this.

Bad Ground Wire Connection Under Fuse Box:

Similar issue here. I had a loose connection of the ground wire under the main fuse box panel in the engine bay. I tightened that ground wire, then disconnected my battery then restarted and it solved the issue.

Loose/Bad ETCS Fuse:

I had a loose 10amp fuse in my ECU slot about a year ago and went into limp mode. After making sure the fuse was back into position, I restarted the 4Runner and everything was fine.

Bad MAF (Mass Airflow Sensor):

I recently went into limp mode and did many of the same troubleshooting techniques seen here but after cleaning my mass airflow sensor and then restarted the 4Runner, the truck returned to normal mode. I would try cleaning the mass airflow sensor, clear any DTCs if you have any, then disconnecting the battery for 5-10 min. Finally, you can restart the battery/4Runner and all should be cleared. Hope this works for you.

Loose Gas Cap (P2121):

Starting about 2 weeks ago I have been getting the check engine light, and the slip indicator car light on every other day, together with a complete loss of power. Ran a diagnose with Carista and got error code P2121. Now when I check that talks about an accelerator pedal position issue. After some research, I simply re-adjusted the gas cap and the problem goes away, clear the codes and all back to normal. However it keeps happening, I tied the gas cap and gets fixed. My actual question, I’m already replacing the gas cap (start with the cheap), and contacted Pedal Commander (they basically told me to send the unit back for an evaluation) Any other ideas? I really hope the gas cap will fix it but wanted to ask around just in case.

Zero Point Calibration – Yaw Rate Calibration

Above is the terminal number layout on the OBD on the 5th Gen 4Runner.

• Toyota TIS (Technical Information System): Toyota Docs on Zero Point Calibration

Here is the step by step process of calibrating the 5th Gen 4Runner with Crawl Control. Although you have three different calibrations, we are only going to calibrate two features (standard and crawl control). Because we don’t have DAC on our 4Runner, we will not be performing the DAC calibration, however, you will find the documentation in the link on this page.

5th Gen 4Runner Calibrations

1. Standard
2. Multi-Terrain Select (Crawl Control)
3. DAC (Downhill Assist Control)

What is An SST Wire?

An SST Wire or SST tool is a “Special Service Tool” that is used as an alternative tool to test the OBD (On-Board Diagnostics) in your 4Runner.

You can buy an actual tool or use something around your garage for free. Other commonly used tools as a direct replacement to an SST are a paper clip or a 12-18AWG wire stripped at both ends (seen above).

Anything larger than a 12AWG wire might not fit. Anything smaller than an 18AWG might not make enough contact or hold its place.

OBD (On-Board Diagnostics)

In order to calibrate your 4Runner, you need to locate your On-Board Diagnostics or “OBD” for short. The OBD is what Toyota technicians connect their software (Tech Stream) in order to pull error codes from your computer (ECM – Electronic Control Module).

In the graphic on the Toyota tech stream docs, you can see the OBD illustration is upside down when compared to the actual OBD in your 4Runner. Just flip the illustration to read the OBD terminals correctly.

Standard Calibration

There are Toyota doc instructions and then there is this detailed version.

NOTES: If the slip indicator light does not blink, perform zero point calibration again. The zero point calibration is performed only once after the system enters test mode. Calibration cannot be performed again until the stored data is cleared.

1. Park on a level surface
2. Center your steering wheel
3. Leave shift level in the park position
4. Ignition switch OFF
5. Ignition switch ON / ACC / Second Position (Do not start the 4Runner)
   1. The ABS warning light and slip indicator light come on for 3 seconds to indicate that the initial check is completed.
6. Insert your SST wires (paper clip or wire) into the #12 and #4 terminal on the OBD reader
7. With the other ends of the wire, you want to connect and disconnect (tap) the wires 4-5 times within 8 seconds.
   1. This will enter you into test mode (ABS and Slip light will blink to confirm test mode).
8. Ignition switch OFF
9. Connect the opposite ends of your SST wires. You should have a wire in the #12 and #4 slot and then the other ends of those wires should be connected (twist them together) to complete the circuit.
10. Ignition switch ON / ACC / Second Position (Do not start the 4Runner)
    1. Keep the vehicle stationary on a level surface for 5 seconds or more.
    2. Check that the slip indicator light comes on and then blink in the test mode pattern (0.125 seconds on and 0.125 seconds off). This will enter you into calibration mode (ABS, Slip, and KDSS light will blink RAPIDLY to confirm calibration).
11. Ignition switch OFF
12. Remove SST Wire
13. Restart 4Runner and drive the vehicle straight ahead at 25 mph or more for at least 10 seconds.
14. Ignition switch OFF
15. START 4Runner

You should have successfully calibrated the 4Runner.

Multi-Terrain Select (Crawl Control) Calibration

You are going repeat steps 1 – 10 from above. Once you enter into step #10 – this will enter you into calibration mode. For crawl control calibration – you are going toggle the multi-terrain select on and the select all modes on the dial and then back to the first position.

1. Repeat steps 1-10 above
2. Turn the crawl ON/OFF switch: Crawl indicator light should come on while the switch is being pushed.
3. Turn the crawl ON/OFF switch off
   1. Turn the speed selector switch to L (low)
   2. Turn the speed selector switch to medium-low
   3. Turn the speed selector switch to M (medium)
   4. Turn the speed selector switch to medium-high
   5. Turn the speed selector switch to H (high)
   6. Turn the speed selector switch to L (low)
4. Ignition switch OFF
5. Remove SST Wire
6. Restart 4Runner and drive on a flat/level surface for 10 seconds
7. Ignition switch OFF
8. START 4Runner

You should have successfully calibrated the 4Runner.

Final Thoughts

The calibration didn’t end up solving our problem, but it might for you depending on your situation.

After taking my 4Runner into Toyota, I did fix my issue. My personal issue was a water leak coming in from the roof of my rack somewhere. I ended up having corroded connector pins that were located in our lower a-pillar kick panel down by the interior fuse box. Water was slowly coming in from somewhere causing corrosion on a few of our ETCS wire pins within the connector.

We had two options (according to Toyota):

1. Rewire multiple harnesses throughout the cabin and into the engine bay (60 hours of labor $9000+ bill)
2. Bypass the connector (6 hours or labor $1000 bill)

I asked if we could just clean or replace the pins in the connector and then reconnect the wires into the connector but apparently there was not enough play in the wires of the harness to cut the wires and extend them back in. Keep in mind this was a tech selling me on the concept, so maybe he just didn’t want to do the work because after looking at it closer, I feel like it could have been done. I ended up having the tech re-route the wires around the connector and straight to the other side of the harness.

Here is what the tech said in his notes:

Found 27 separate codes stored throughout the system. Throttle is unresponsive. Need more information up to this point, what preceded all conditions and also who has been attempting repairs. What repairs have been done, and if any recalibrations have been done. Found .5 V at ECU terminal for a ETCS fuse. Followed system circuit error and found in lower kick panel connector FA2 has corroded terminals and several circuit errors. Recommend repair wiring by bypassing connector and recheck. Tech bypass affected wires in connector FA to located in lower kick panel. Pin fit tested and clean connector, evaluated condition of all connectors and connector F82. Found three wires that have excessive corrosion they could not be cleaned and had loose pin fit. Installed bypass wires using solder splices and heat strength. Covered with approved cloth electrical tape after repairs. Test drove 5 miles and 4Runner drives good after repairs. No warning lights on at this time and engine power feels normal at this time.

What did I learn? 

I learned more about my 4Runner, the parts within my 4Runner, the ETCS, how the parts are connected (throttle body, actuator, ECM, pedal, etc.) and how to troubleshoot a little deeper throughout the 4Runner. Also, the takeaway here is to SEAL EVERY SINGLE AREA on the roof rack mounting points – just in case that is your issue.

Comment below with your situation, and how you solved it, you may just help someone else.