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P1670 Code on 7.3 Powerstroke: Meaning & How To Fix

Powerstroke engines have served truck lovers for decades. Though the 7.3 Powerstroke is no longer in production, many trucks still have it, and as their owners try to keep them well-maintained, many find themselves dealing with a P1670 error code. What does this mean, and how can it be fixed?

The P1670 code on a 7.3 Powerstroke indicates a break in communication between the IDM (Injector Driver Module) and the PCM (Powertrain Control Module). Possible fixes include replacing fuses and relays, checking and fixing wiring problems, and replacing the IDM.

In this article, we’ll look at issues that can cause the P1670 error code and possible fixes. I’ll also provide you with tips on how to care for your 7.3 Powerstroke engine so you can avoid errors in the future. Let’s get started.

What Does a P1670 Code on a 7.3 Powerstroke Mean?

The P1670 error code indicates that the IDM and the PCM are not communicating as they should. Ideally, there is an exchange of electric feedback between the IDM and the PCM.

If this exchange is missing or hampered, it will result in some issues that trigger the P1670 error code.

How To Fix a P1670 Code on a 7.3 Powerstroke

Some of the problems that can bring up a P1670 error code include the following:

  1. Open or shorted fuses
  2. Faulty Injector Driver Module
  3. Fuel Delivery Command Signal (FDCS) with a shorted or broken circuit
  4. Electric feedback circuit with a broken or shorted connection

The first step to fixing any issue that results in a P1670 error code is identifying the exact cause of the error. There’s no one-size-fits-all solution for this error, so we shall look at some possible fixes that you can explore.

The four possible fixes I will discuss below can apply to some or all of the problems mentioned.

1. Carry Out a KOEO Self-Test for Associated Problems

The P1670 error code may be just one of many others issues related to a faulty IDM.

Unless you carry out a comprehensive KOEO (Key on, Engine off) self-test, other diagnostic error codes associated with the IDM may not be discovered.

This video shows how to carry out a KOEO self-test:

You can also conduct a buzz test to identify other errors that may exist on your 7.3 Powerstroke. For a visual guide of how to perform a buzz test easily, watch this video: 

If you find more error codes that you may not fully understand, you can look them up or call on your service expert.

2. Replace the IDM

Replacing the IDM is likely to resolve the P1670 error code completely, assuming that the problem is not beyond the IDM.

While there may be less expensive fixes, replacing the IDM can be a faster and easier fix if you do not mind the cost.

Should you decide to replace your Injector Drive Module (IDM), you will find step-by-step instructions in this video: 

3. Check the Wiring Harness for Shorting and Disconnection

A P1670 error code can also indicate issues in the wiring harness that connects the IDM to the injector. If this is the case, you may be dealing with damage to the fuses or the IDM itself.

When checking for shorting and disconnection in the wiring, you’ll need to clean out the wires and replace damaged ones.

Prompt replacement of damaged wires is highly important because faulty wire connections can further damage your system. Faulty writing can also cause problems in a newly replaced IDM.

To see how you can check and troubleshoot the wires, watch this video: 

4. Check and Replace Faulty Relays and Fuses

Fuses are essential safeguards that protect against electrical damage. They work to regulate the flow of electricity and prevent an overload from damaging the wiring.

When a fuse fails, a power surge can pass through your system and damage the IDM. If this happens, you’ll have an open circuit that will need to be bridged with an appropriate fuse.

Replacing a faulty fuse can restore your damaged system. You may also need to check for faulty relays, which help automate the connection between your IDM and the PCM.

Faulty relates cause inefficient communication between the IDM and PCM, resulting in a malfunction. Replacing all faulty relays and fuses may solve your P1670 error code issue.

However, I suggest that you change relays and fuses after you’ve checked the wires and made sure that they are in good condition. If you plug in new relays and fuses into a system with wire issues, you may just find yourself new faulty relays and burnt fuses.

Note that your vehicle doesn’t need to have all the issues listed above for the P1670 error code to be triggered. Any one of these issues can trigger this error code.

If you try all of the fixes suggested above and still have issues, then it may be time to get a professional mechanic to help you out.

Signs of a P1670 Error Code Issue

There are many signs that point to a P1670 code-related issue. Once your vehicle exhibits any of these signs, quickly run a scan and see if you are dealing with any of the previously mentioned issues.

The following are some of the signs that can be indicative of a P1670 error code:

  • Check engine or service engine soon light – It should be a standard practice that once your “check engine” or “service engine soon” light comes up, you quickly find out what the issue is. Doing so will help you catch early faults and fix them before they become more serious.
  • Engine not starting – If your car is not starting, it may just be because a problem has developed in the communication lines between the IDM and the TCM.
  • Irregular RPM – Once you notice that your vehicle has an irregular RPM (Rotations Per Minute), which will translate into an undulating engine sound, you should run a scan to know if you will get a P1670 diagnostic error code.

How To Care for Your 7.3 Powerstroke Engine

As with all engines, you can only get the best from your 7.3 Powerstroke when you take good care of it.

While taking proper care of your 7.3 Powerstroke does not guarantee that your engine will never throw up the P1670 diagnostic error code, it will at least ensure that your truck works smoothly.

Service Your Vehicle On Time

It is recommended that you perform general servicing of your 7.3 Powerstroke-powered vehicles after 5,000 miles (8,047 kilometers) of regular use or after 3,000 miles (4,828 kilometers) of heavy use. This should include a change of oil and oil filter.

Below is a breakdown of recommended service times:

  • The fuel filter should be changed after 15,000 miles (24,140 kilometers) and the air filter after 30,000 miles (48,280 kilometers) or 30 months, whichever comes faster. Of course, if the dashboard warnings for any of the two above comes on before the stipulated time, then you should, of course, change them.
  • At 50,000 miles (80,467 kilometers), change your coolant. You should completely flush out the old coolant. After this, subsequent flushes should be done every 30,000 miles (48,280 kilometers).
  • The ATF and filter should be replaced after 30,000 miles (48,280 kilometers) of regular use and after 21,000 miles (33,796 kilometers) of intensive use.
  • Manual transmission fluids should be replaced after 60,000 miles (96,561 kilometers).
  • Auto transmission shift linkage should be checked and lubricated after 5,000 miles (8,047 kilometers) of regular use and after 6,000 miles (9,656 kilometers) of intensive use. Subsequent checks and lubrication should occur every 10,000 miles (16,093 kilometers).
  • The clutch release lever should be checked and lubricated after 5,000 miles (8,047 kilometers) of regular use and 3,000 miles (4,828 kilometers) of intensive use. Subsequent changes can be done every 15,000 miles (24,140 kilometers).
  • Transfer case fluid should be replaced after 60,000 miles (96,561 kilometers).
  • Front and rear differential fluid should be replaced after 99,000 miles (159,325 kilometers) of intensive use or after 30,000 miles (48,280 kilometers) of regular use. If, however, the vehicle is submerged in water, you should change this fluid immediately.

Use the Right Oils and Replacement Parts

It’s one thing to stick to the correct service schedules and another thing to use the right oils. Using the wrong oil for your engine or transmission can cause problems for your vehicle.

Since there are many oils and parts to consider, you can find an extensive list of the recommended oils and parts here.


The P1670 error code in your 7.3 Powerstroke engine appears when there’s miscommunication between the injector driver and the powertrain control module.

To resolve this issue, check for any problems related to the following:

  • Shorted fuses
  • Damaged wiring
  • Faulty IDM

By servicing your vehicle on time and being aware of signs of trouble in your 7.3 Powerstroke engine, you can prevent problems that lead to a P1670 error code.

Other 7.3 Powerstroke error codes and how to fix them: