Generic OBDII P Codes P0700-P0799: Definitions and causes

Learn the code definitions and most common causes for Generic OBDII P Codes P0700-P0799

This post lists the most common trouble codes in the OBDII P Codes P0700-P0799 category. These are transmission-related trouble codes. Read the most common codes and causes, and then refer to the code chart at the end of the post for official code definitions.

I’ll start by discussing the most common Trouble codes in this group and their most common causes. For a full list of the codes in this group, scroll to the bottom of this article.

How to find P Codes P0700-P0799

There are 185 700-series codes. There are several ways to find the code definition in the chart below.

1) Enter the trouble code in the search box. That’s the fastest way
2) If you’d like to scroll all the codes, change the Number of entries to show on the page in “Show Entries” box. Click NEXT or PREVIOUS at the bottom right of the table

This graphic shows the three ways you can navigate the refrigerant chart: 1) Increase the number of entries, enter the year of your vehicle in the search box, or scroll the chart using the next/previous buttons at the bottom of the chart

Learn the most common codes in the P0700-P0799 category

A P0700 Transmission Control System Malfunction is a very common code

Not all vehicles use a transmission control module  (TCM). Some vehicle use a powertrain control module (PCM) that controls engine operation and transmission operation. If you see this code it means your vehicle has a separate engine control module (ECM) and a transmission control module (TCM).

In most cases, a P0700 code means there’s a problem with the (TCM), the wiring harness to the TCM, or a problem in the data line between the ECM and the TCM.

Diagnosing a P0700

Always start diagnosing a P0700 by checking for good power and ground to the TCM and by checking the data line between the ECM and the TCM. If those are good, chances are high that the TCM is bad. Your options for replacing the TCM are to get a new one from the dealer or to send your existing one out to be rebuilt and reprogrammed.

I personally recommend the rebuilt route. Rebuilding your existing TCM will save a lot of money, and the rebuilder can program it to your vehicle’s VIN number. One rebuilder I recommend is modulemasters com.

P0705-P0709 Transmission Range Selector Sensor Circuit Malfunction codes are very common codes

P0705 Transmission Range Sensor A Circuit malfunction

Transmission range selector (TR)

(PRNDL Input), P0706 Transmission Range Sensor A Circuit Range/Performance, P0707 Transmission Range Sensor A Circuit Low Input, P0708 Transmission Range Sensor A Circuit High Input, P0709 Transmission Range Sensor A Circuit Intermittent

A transmission range sensor is a modern name for what everyone used to call a park-neutral switch. Since most modern transmissions are electronically controlled, the transmission range sensor uses a series of resistors that vary the voltage to either the PCM or the TCM, telling the transmission which gear the driver has selected. Over time, with corrosion, the transmission range sensor can’t deliver conflicting or false data.

How to diagnose P0705-P0709 codes

I suggest purchasing a subscription to a chop manual like alldatadiy.com or eautorepair.net To find the resistance values for each gear selection. Then use a multimeter at the transmission range sensor to determine if the sensor is giving the correct readings. If not, the sensor is bad and is a common failure point.

P070A-P070F codes are becoming more common

P070A Transmission Fluid Level Sensor Circuit, P070B Transmission Fluid Level Sensor Circuit Range/Performance
P070C Transmission Fluid Level Sensor Circuit Low, P070D Transmission Fluid Level Sensor Circuit High, P070E Transmission Fluid Level Sensor Circuit intermittent/Erratic, P070F Transmission Fluid Level Too Low

Most modern transmissions no longer have a dipstick. Carmakers eliminated the dipstick because too many DI wires were adding the wrong type of transmission fluid. That doesn’t mean you can’t check the level of your transmission fluid, however. You can but you must remove the seal on the fill port and check the level from underneath the vehicle.

On modern CVT transmissions fluid level is critical to the operation and lifespan of the transmission To avoid running the transmission when it’s low on fluid or overfilled carmakers have installed fluid level sensors. These codes relate to fluid level and our critical codes. If you receive one of these codes you must check and add fluid immediately to avoid damaging the transmission.

Refer to a shop manual to learn how to check the fluid level on your vehicle.

Codes P0720-P0723 are also common codes

P0720 Output Speed Sensor Circuit Malfunction, P0721 Output Speed Sensor Range/Performance, P0722 Output Speed Sensor No Signal, P0723 Output Speed Sensor Intermittent

The PCM or TCM know the input RPM to the transmission, knows which gear has been selected, and expects to see a certain rotational speed of the output shaft. If the output shaft speed isn’t what the computer expects, it sets one of these codes.

How to diagnose P0720-P0723 codes

The problem with diagnosing these codes is that the cause can be a bad sensor or slipping clutches inside the transmission. You can’t know if there’s internal slippage until you know if the sensor itself is good . Aside from checking the resistance of the sensor, there’s no other way to check it except to replace it with a known good sensor . I have to warn you, though, that most aftermarket sensors are low quality . If you’re going to replace the sensor, I highly recommend that you buy it from the dealer

P0740-P0744 are common codes

P0740 Torque Converter Clutch Circuit Malfunction, P0741 Torque Converter Clutch Circuit Performance or Stuck Off, P0742 Torque Converter Clutch Circuit Stock On, P0743 Torque Converter Clutch Circuit Electrical, P0744 Torque Converter Clutch Circuit Intermittent

These codes relate to the torque converter clutch solenoid. This solenoid opens a pressure port to send high-pressure transmission fluid to the lock-up clutch inside the torque converter. The pressure locks the clutch and puts the transmission into overdrive. If you get one of these codes, it can mean the solenoid has failed or a check ball in the valve body is sticking and not allowing the fluid to get through to the clutch.

How to diagnose these codes

Using a shop manual and a multimeter, you can test the solenoids for an open condition, a short-to-ground condition, or low or high resistance. Unfortunately, there’s no way to check for a stuck valve body check ball without actually opening the transmission

The most common cause of these codes is a bad torque converter clutch shift solenoid.

P0750-P0744 codes are the most common transmission codes

Carmakers use a series of electrically operated solenoid valves to pulse oil pressure into the bands and clutch packs of an automatic transmission. Because these solenoids open and close at high speeds, they have a fairly high failure rate. However, the same solenoids can malfunction if the transmission has been neglected and the transmission fluid has degraded, overheated, and turned to varnish.

Many DI wires replace individual shift solenoids or solenoid packs only to find the same codes popping up. This usually means there are other problems going on inside the transmission that are preventing proper fluid flow to the bands and clutches.

Rick’s advice for dealing with shift solenoids

I found that there’s a huge difference in quality between aftermarket solenoids and solenoid packs compared to dealer parts. Instances where I’ve replaced a solenoid pack with an aftermarket pack, gotten the same trouble code and then replaced it with a dealer part and the trouble cold disappeared.

Since replacing solenoid packs can be a big job I always recommend using OE parts from the dealer.

The three ways you can replace solenoids: replace an individual solenoid, replace a solenoid pack, or replace the entire valve body

©, 2024 Rick Muscoplat